NEWS alleged to contain 84 of caseine, very nearly the entire fat must have been weighed with the caseine. This instance of official ignorance speaks volumes, and calls for the interference of the Government. Soluble Glass in the Arts.-The employment of this substance in the arts is rapidly extending, and it has become indispensable in many industrial branches. It seems to be specially well adapted to the production of cements; when intimately mixed with fine chalk, it is found that a hard cement will be formed in from six to eight hours. With powdered sulphide of antimony, a black mass is produced, which is susceptible of taking a high polish, and possesses then a superb metallic lustre. Fine iron-dust gives a grey-black mass of great hardness. Zinc-dust gives a grey mass of much hardness, and having a metallic lustre. Zinc castings can be readily repaired by its aid. Journal of the Franklin Institute. PATENTS. ABRIDGMENTS OF PROVISIONAL AND COMPLETE SPECIFICATIONS. Improvements in the production of colours for dyeing and printing. Edward Chambers Nicholson, Herne Hill, Surrey. October 19, 1872; -No. 3094. In the production of colours from aniline it is the general practice to employ what is known as arsenic acid, which when heated with aniline produces colouring matters which have as their base rosaniline. Now this invention relates to the substitution of arsenic acid in and for the production of colours from aniline of nitric acid and of hydrochloric acid, by the employment of which acids in conjunction with an excess of aniline and upon the application of a sufficient and prolonged heat, viz., of a temperature of about from 350 degrees to about 400 degrees Fahrenheit, to such mixture or combination, the desired colouring matters are produced. In carrying out my invention I take about 3 parts by weight of commercial aniline, such as is now generally employed for the production of red aniline dyes, and I add thereto about 1 part by weight of nitric acid of about the specific gravity 1420 and about 1 part by weight of hydrochloric acid of about the specific gravity 1160, the mixture or combination being contained in a boiler or other suitable vessel. I heat the same to a temperature of from about 350 degrees to about 400 degrees Fahrenheit until the conversion of the aniline and the compounds of aniline unto the desired colouring matters is effected, which result can be ascertained by occasionally testing the contents of the boiler. I have mentioned the temperature of about 350 degrees to about 400 degrees Fahrenheit as I find that the employment of such an elevated temperature is much more advantageous than the employment of a lower temperature, such for example as a temperature of 212 degrees Fahrenheit or the temperature of boiling water. Having effected the desired result, the contents of the boiler or other suitable vessel are removed and the colouring matters extracted therefrom by means of boiling water or other solvent, and the colouring matters thus separated may be either employed direct or may be subjected to purification, or the base, viz., rosaniline, may be separated therefrom by means of an alkali or of an alkaline earth as is well understood. I wish it to be understood that although I have given the proportions with which I have obtained good results I do not limit myself to such, as they may be modified. Improvements in the treatment of substances capable of being employed for the purposes of dyeing and printing. Astley Paston Price, consulting chemist, 47, Lincoln's Inn Fields, Middlesex. October 19, 1872.-No. 3095. In the production of what is known as red aniline dyes from aniline, the method generally adopted is to heat together a mixture of aniline, or that substance which is known as commercial aniline and arsenic acid, until the desired colours are produced. The result thus obtained is known technically as the "melt," and the subsequent treatment or purification of the melt is generally conducted as follows:-The melt is digested in boiling water, and in some cases the solution is filtered and allowed to cool in order to separate what is known as arseniate of rosaniline and other compounds. The supernatant solution, or the original solution of the melt, is treated with lime in order to separate the arsenic and the arsenious acids which exist in the solution either in combination with rosaniline or with other colouring matters or otherwise. The liberated base, or what is known as rosaniline base, is then dissolved out by means of hot water, and is separated by crystallisation. By this process the arsenic and the arsenious acids are converted into arseniate and arsenite of lime, and thus rendered insoluble, and hitherto these products have been of no practical value. Now this invention relates to the treatment of the before mentioned product, or the result of heating aniline with arsenic acid and known as the "melt," in such a manner as that the arsenious and the arsenic acids contained in the solution of the melt shall be obtained in an available condition, and not as hitherto as a compound of lime possessing but little, if any, commercial value, and it consists in adding to the solution of the melt such an amount of ammonia or of ammoniacal liquor, as shall liberate the rosaniline base existing in such solution in the form of arseniate or arsenite of rosaniline. After allowing the base thus liberated to separate from the solution, the said solution contained in a suitable distillatory apparatus is submitted to the action of heat, either by applying heat externally or internally, or by the injection of a jet of steam, or otherwise. The compound of arsenious acid and ammonia is thus decomposed, and ammonia is liberated, which after having been collected may be again employed or otherwise utilised. The arsenious acid remaining in the solution may be separated therefrom by evaporation and crystallisation, or otherwise. In this manner the arsenious acid may be recovered in a condition capable of being which had not been previously separated by crystallisation, as arseniate re-converted into arsenic acid as is well understood. Any arsenic acid of rosaniline, will be found to be contained in the residual solution after having effected the decomposition of the solution of arsenite of ammonia by the employment of heat, and such arsenic acid or arseniate of ammonia may be separated either by evaporation or by evaporation and crystallisation. Improved processes and apparatus for manufacturing compounds of pyroxyline or gun-cotton. William Robert Lake, patent agent, Southampton Buildings, London. (A communication from John W. Hyatt and J. Smith Hyatt, Albany, New York, United States of America). October 21, 1872.-No. 3101. This invention relates to the conversion and manufacture of pyroxyline or soluble cotton into a general process described in the Specification of Letters Patent, dated solid (which is herein denominated "celluloid") in accordance with a April 18th, 1871, No. 1025, to which Letters Patent reference is here made for a full description of the said process. This invention consists in the method or process of drying the prepared mixture of soluble cotton and camphor gum. In the process of manufacturing celluloid. In the process of dissolving or transforming pyroxyline. In the arrangement of a cold water jacket around the upper portion or receiving end of the heated converting cylinder. In the combination with a converting cylinder provided with a cold water jacket of a steam or hot water jacket. In the arrangement with the cold water jacket of the escape pipe of the hydraulic engine. In the arrangement with the upwardly projecting piston rod of the hydraulic engine and the supply and escape pipes thereof of two three-way cocks. In the arrangement in the discharge end of the converting cylinder of a central heating and distributing core; and in the combination with the hydraulic engine, converting cylinder, and celluloid discharge pipe of a mould and hydraulic clamp. W. Ripley Nichols.-The copies have been received, and one forwarded to Prof. Wanklyn. R. Riley. It is published weekly; S. Low and Co., Crown Buildings, Fleet Street, will procure it for you. Goldsmith.-Pure hydrochloric acid will answer the purpose. G. Procter.-The work is still in the press. 3. E. K.-See CHEMICAL NEWS, vol. xxv., pp. 166, 178, 242. 7. S. W.-There is no later edition of the work you mention; it is the best book you can have on the subject. A work on dyeing will shortly be published, which will also be useful to you. BERNERS COLLEGE of CHEMISTRY.— EXPERIMENTAL MILITARY and NAVAL SCIENCES, under the direction of Professor E. V. GARDNER, F.E.S., &c. of the late Royal Polytechnic Institution and the Royal Naval College The Laboratory and Class Rooms are open from 11 to 5 a.m., and and from 7 to 10 p.m. daily. Especial facilities for persons preparing for Government and other examinations. Private Pupils will find every convenience. Analyses, Assays, and Practical Investigations connected with Patents, &c., conducted. For prospectus, &c., apply to Prof. E. V. G., 44, Berners-street, W. May 23, 1873. Extract from Analytical Report by WENTWORTH L. SCOTT, Esq., F.C.S., &c.:-"The simplest, safest, and most effective means for the 'preservation of animal substances.' Medlock & Bailey's Patent Bisulphite of Lime, For the Preservation of Meat, Fish, Poultry, Game, and all other Animal Substances, IN TEMPERATE OR TROPICAL CLIMATES, AND ON BOARD SHIP. By the use of this valuable Preparation fresh Meat can be had throughout a voyage, however long, thus avoiding the expenses and losses incidental to the conveyance of live stock on board. No steamer or passenger ship should be without it, as it will enable captains to lay in provisions at foreign ports, wherever they are cheap and good, relieving them of the necessity of providing for the voyage home. It imparts no flavour to the meat, nor does it lessen its nutritive value, while it prevents scurvy and destroys contagion wherever it is used. For further particulars, see Descriptive Pamphlet, and also Opinions of the Press, both sent post free for seven stamps. Extract from the "Times" Money Article of December 10, 1870. "There was a trial of Preserved Meat from Rosario, in the Argentine Republic, in the City on Wednesday, with, it is stated, most satisfactory results. The preparation was effected by immersion in a solution of Bisulphite of Lime, according to the process of Messrs. Medlock and Bailey, of the Horseley Fields Chemical Works, Wolverhampton, and the meat was sealed up in a cask in the presence of Mr. Hutchinson, the British Consul at Rosario, on the 10th of August last, and brought by him to this country in a recent steamer. It had, therefore, been kept four months, and had made a passage across the Line, yet was found perfectly fresh, not only in quality, but in appearance, and was deemed by the persons present at the trial equal to any good ordinary home beef. Amongst these persons were merchants largely interested in the commerce of the River Plate, by whom an unqualified conviction has since been expressed that the problem of bringing unlimited supplies of animal food from distant regions will now prove to have been solved, the method being alike simple and inexpensive, and capable of being adopted under any circumstances. At the trial on Wednesday not the slightest flavour of any chemical or other artificial agent was detected." The meat was cooked at SIMPSON'S, Bolt Court, Cornhill, and was partaken of by a number of influential gentlemen and merchants interested in the question, including M. B. Simpson, Esq., Consul-General of the Argentine Republic; Consul-General Neil, of Uruguay (copies of whose Official Certificates can be had on application), &c." Extracts from a few of the communications lately received by the Patentees. SIR JAMES MATHESON, Bart., M.P., July 20, 1868, enclosing a further order:-" Sir James Matheson is glad to tell Messrs. William Bailey and Son that their Bisulphite of Lime answered perfectly in carrying the carcases of a deer and a calf from Stornaway to London, quite fresh, being on the journey and voyage four days, during the very hot days of June; besides enabling the venison and veal to be kept twelve days after arrival by using the Bisulphite according to directions." MR. GEORGE BLACKMAN, Butcher, of Newport Market, London: "I find Medlock & Bailey's Patent Preserving Liquid invaluable." MR. GEORGE SCARLETT, Butcher, of Notting Hill, London :-"I believe there is nothing to be compared with your Bisulphite." THOMAS J. HUTCHINSON, Esq., F.R.G.S., F.A.S.L., Her Britannic Majesty's Consul for Rosario, Rio de la Plata:-"When at Monte Video, I had the pleasure of tasting at breakfast a small piece of beef prepared by the Bisulphite of Lime, sent out to the Plate. It was given to me by Mr. Prange. The preservation of that meat was perfect, and it was the first piece of real juicy beef that I have tasted for the last seven years." DR. STONE, Health Officer, Trinidad :-" I have found your Bisulphite of Lime of great value as a means of preserving meat." THE GOVERNOR OF THE CITY POOR HOUSE, Edinburgh, "is very highly pleased with the results obtained from the use of your Bisulphite." MR. ALEXANDER M'ALLISTER, Fish and Game Salesman, of Glasgow :-" By your Patent Process I have succeeded quite beyond my most sanguine expectations." THOMAS SUTTON, Esq., B.A., of Redon, France, August 27, 1868:"At last I have tried your Bisulphite of Lime, and I find it a grand success. We dined yesterday off a leg of mutton which I had preserved, and found it delicious-undistinguishable from fresh meat-no flavour of the Preservative-rich red gravy-no loss of weight. Every word is true that you say in your Pamphlet." MESSRS. HOPER & SCHWERIN, of Berlin, September 17, 1868:-"We have much pleasure in informing you to-day that our success with meat as well as beer has been complete beyond expectation." In addition to its remarkable powers in preserving animal substances from decay, MEDLOCK & BAILEY'S Bisulphite of Lime is also an absolute specific against epidemic Cattle Disease if used in accordance with the Patentees' instructions. It thus enables the Shipper to carry either live or dead" meat in perfection without fear of loss in transit from the bad health of the one or the decomposition of the other." Sole Manufacturers-Messrs. WILLIAM BAILEY & SON, Horseley Fields Chemical Works, Wolverhampton; and 2 & 3, Abchurch Yard, Cannon Street, London, E.C. MR. J. W. SALISBURY, Meat Salesman, of Newgate Market, London:"It is a most valuable thing for butchers." The GENUINE Bisulphite of Lime of Medlock and Bailey ONLY should be used. Price, 3s. 6d. per gallon, packages included. Now ready, our New Revised TO MANURE MANUFACTURERS. CATALOGUE OF CHEMICALS AND CHEMICAL The Lincolnshire Farmers' Association is APPARATUS, Also SCALE OF ANALYTICAL FEES, PHILIP HARRIS & CO., Manufacturing Wholesale and Retail Chemists, BULL RING, BIRMINGHAM. Just Published, fcap. 8vo., limp cloth, illustrated, 2s. 6d. post free, desirous of receiving TENDERS for the supply of the PHOSPHATIC MANURE required by its Members during the next year. Several thousand tons of the Manure will have to be supplied; it must contain 26 per cent of soluble phosphate; and must be delivered (free of carriage) at the Depots of the Association at Grimsby, Gainsborough, and Sutton Bridge, either by sea or otherwise, and at Lincoln and Peterborough, in good, dry, and friable condition, for sowing by hand or with the dry drill. Manufacturers willing to tender for the supply of the Manure at all, any, or either of the Depots, can obtain full particulars, as well as to the probable quantity required at each Depot, and the times and modes of delivery, as in all other respects, on application to me. Tenders, addressed to the Chairman and endorsed "Tender for Superphosphate," must be sent in, under cover, to me not later than Practical Examples in Quantitative Analysis; Friday, the 30th inst. forming a Concise Guide to the Analysis of Water, &c. By ERNEST FRANCIS, F.C.S., Demonstrator of Practical Chemistry, Guy's Hospital. London H. K. LEWIS, 136, Gower Street. RESPECTFUL given by LIEBIG'S EXTRACT OF MEAT COMPANY (Limited) that the Guarantee Certificate of Genuineness of Quality, signed hitherto by Baron Liebig and Professor Max von Pettenkofer, will in future, in accordance with Baron Liebig's own directions made many years ago, be signed by his Colleague, Professor Max von Pettenkofer, the eminent Chemist, and by Hermann von Liebig, son of Baron Liebig, who has been acting as his special assistant in the Analysis of the Company's Extract. Thus the excellence of the well-known standard quality of Liebig Company's Extract of Meat will continue absolutely unaltered. By order of the Committee, C. E. BISSILL, Solicitor and Secretary. [tilisation of Sewage and Purification of No. 1, Crown Buildings, Queen Victoria Street, London, E.C. SCIENTIFIC PRESENTS.-Collections to Illustrate "Lyell's Elements of Geology," and facilitate the important study of Mineralogy and Geology, can be had at 2, 5, 10, 20, 50, to 500 guineas; also single specimens of Minerals, Rocks, Fossils, and Recent Shells. Geological Maps, Hammers, all the recent publications, &c., of J. TENNANT, Mineralogist to Her Majesty, 149, Strand. Private Instruction is given in Geology and Mineralogy by Mr. Tennant, F.R.G.S., at his residence, 149, Strand, W.C. THE CHEMICAL VOL. XXVII. No. 705. inverted, and the tube with its brush of cotton-wool NEWS. plunged into the fluid to be filtered, taking care that the ON A NEW MODE OF FILTRATION. By ISAAC B. COOKE. THE method of filtering, in which Bunsen has availed himself of Sprengel's water-air pump, is doubtless a great improvement upon the simple paper system: both in the time saved, and in the state in which the precipitate is left. But the pump is a comparatively costly apparatus, and not always suited to the position and circumstances of a private laboratory; and as the same, or nearly the same, effects can be produced by means which are in every chemists' hands, the plan here proposed may be convenient for some. The needs of chemists have caused the manufacture of a special paper fitted for most of their filtering operations. But in some cases the texture is too coarse, and in some too fine. When a large sized filter is used the ash is too uncertain, and too great for nice quantitative operations. A small size requires constant and long-continued attention in order to pass through it even a reasonably small quantity of filtrate, together with the requisite washings. In the process here advocated a quantity of carded cotton-wool, so small that the ash does not weigh 100 grs., and in commercial analyses may therefore be generally neglected, will suffice for any ordinary filtration; and a little experience enables the operator, by tight or loose packing, to adopt it to the coarsest or finest precipitate. A glass flask, of not more than about 300 c.c. content, is fitted with a rubber stopper of soft and smooth surface, and of conical shape, so that the small end easily enters the neck of the flask; but the larger end cannot be forced in even under considerable pressure. Through the centre of the stopper a hole is bored to admit of a glass tube of aboutths inch internal diameter. The tube to be inserted should be about 6 inches long; one end being fused to a very small opening, and the other slightly enlarged in funnel form. About 1 inch of the nearly closed end of the tube is passed through the stopper, fitting tightly; and if an inch traverse the stopper 4 inches will be left outside when the stopper is in its place. Into the funnel-shaped mouth of the tube a small quantity of the carded cotton-wool is packed with the tapering end of a wire not having too sharp a point. The cotton-wool should be lightly pressed in at first until it occupies a length of about to inch of the tube, and then may be pressed more tightly at the mouth according to the quality of the precipitate to be filtered off, leaving a spreading brush of about inch length projecting from the end. To put the instrument into operation a small quantity of distilled water is poured into the flask sufficient, but not more than sufficient, to quite cover the inner convexity of the bottom. The flask is then placed over the lamp till the water boils freely, and all air is expelled from the flask by steam. During the boiling the stopper should be placed in an inclined position, the short end of the tube resting against the inside of the neck of the flask, so as partially to close it, but leave space for the air and steam to rush out. Unless the mouth of the flask is thus partially closed during the boiling a much longer time is required to drive out the air; as if quite open a circulation takes place, cold air passing in at one side as steam is driven out at the other. wool is wholly submerged; as if any portion be left dry protruding from the fluid air will be drawn through it into the flask. As soon as the fluid is seen to be rising up the tube, the apparatus may be reared against a corner and left to itself. When steam issues freely past the sides of the stopper the flask may be taken from the lamp, and the stopper immediately pressed into its place and kept there by pressure until condensation begins. The flask is meantime The filtration will proceed with more or less rapidity in proportion as the cotton is packed lightly or solidly into the tube. When all the liquid has been drawn up, and the air is about to follow, a stream of distilled water from the wash-bottle may be driven upon the precipitate to wash it; and as the last portion of this also passes up the washing can be repeated, and again as often as is thought necessary. Lastly, the air following will leave the precipitate and the cotton-wool in a condition almost dry. The contracted orifice of the inner end of the tube secures it also free from fluid. It is generally advantageous to perform the filtration from a small porcelain evaporating basin of about 2 inches diameter, supported on a cork ring. The fluid and precipitate can be gradually poured and washed into When it is completed the basin as the process goes on. the flask may be reverted, the stopper gently loosened, and the inner end washed by a stream from the washbottle into the flask. The cotton plug must now be carefully taken out by forceps over the evaporating basin, partially wiping the end of the tube in doing so with the clean portion of the plug, and the whole added to the precipitate. The forceps should be carefully wiped with a very small piece of cotton-wool, which may be further used with the forceps to complete the cleaning of the tube, and then also added to the precipitate. The basin after being rapidly dried over the lamp is ready for ignition. The precipitate cannot well be separated from the plug without loss; but there are few cases in which it will be injured by being ignited with the small quantity of cotton of which the plug consists, or, at least, in which that injury cannot be remedied by re-ignition after treatment with nitric or sulphuric acid. On cooling, the basin and its contents can be weighed, and, after brushing out the ash, the basin alone; the difference of course being the weight of the ignited ash. A flask of 100 to 150 c.c. capacity is usually sufficient for a filtration; but it is not safe to use one larger than 300 c.c. unless it be of a spherical shape without the flat or concave bottom, as larger ones are not always proof against the pressure. A spherical flask would be better also in respect of requiring a smaller quantity of water to drive out the air, and, therefore, also a shorter time to prepare it. In this case, however, if only a small part of the surface of the bottom is covered with fluid, care is required not to crack the flask during the boiling. If the stopper be pliable, smooth, and well fitting, no air will pass between it and the neck of the flask during the operation. But the appearance of such leakage is stimulated by the renewed boiling of the fluid in the flask in consequence of the diminished pressure. Unless the fluid to be filtered has been boiled immediately preceding bubbles of air will constantly ascend the tube during the process. Yet the vacuum caused by the initial boiling will be so nearly completed that the filtration and washing may be continued if necessary till the body of the flask is nearly filled with fluid, and on reversion only a portion of the neck will be occupied with air. When a flask is found unexpectedly not to be large enough to contain all the fluid required by the washing, it is better to suspend the filtration before the flask is full, and raising it out of the fluid to allow air to pass up the tube before reverting. The plug will then be in a dry state, and no portion of the fluid will run down the outside of the tube and be lost. Another flask in which the same stopper fits may be prepared by boiling, the tube inserted, and the filtration completed. | position, is placed near a window; the tubes filled up to the 10-inch mark with the solutions from the respective flasks, and then inclined towards the light at such an angle that by adjusting the mirror the operator looking close down upon the latter can see most clearly the reflection of the disc of colour. Should these discs agree in tint, the operation is over, and the estimation can be arrived at; but this is far from likely to be the result of a first trial, and here the use of the apparatus will be apparent. The column of deepest tinted liquid must now be lowered by returning it to its proper flask until the tints of colour as seen in the mirror exactly agree, and this can be done to the greatest nicety. The tubes are now replaced in a vertical position, and the height of the columns of liquid read off. Now putting a for the height in inches of liquid in tube A, b number of c.c. of standard NH3 used in making the trial solution in flask B. The quantity of the latter in c.c. which should be used for the next trial solution is manifestly expressed by the formula— b a C ON SOME IMPROVEMENTS IN THE MODE OF ESTIMATING AMMONIA BY THE "NESSLER" TEST. By SIDNEY HARVEY. THE wonderful delicacy of the Nessler test when used for the detection and estimation of traces of ammonia seems to deserve a more exact method than that usually adopted, viz., the comparison of the depth of colour produced by this reagent in solutions of known and unknown strength in glass cylinders filled to a certain height. Having been much engaged for some time past in the estimation of ammonia in waters, I have devised the following simple apparatus for its more exact and speedy accomplishment, and which answers its purpose remarkably well. Two white glass tubes like test-tubes, but longer and of stouter glass, about inch internal diameter, and between II and 12 inches in length, are mounted upon a stand as shown in the sketch, and by means of pivots can be fixed either in a vertical position or swung to any convenient angle. These tubes are each divided by a paper scale or otherwise into inches in length, reckoning from the bottom, being graduated to contain 10 inches depth of fluid; they should also be marked respectively A and B. The cross-bar, c, should be perforated with two holes to admit the lower ends of the tube, which latter should be parallel, and not more than 1 inches apart, reckoning from centre to centre. The holes should pierce the bar, and be contracted to -inch diameter at bottom. The under surface of the bar should be blackened; and below it in a convenient position should be fixed a small plateglass mirror (D) about 5×3 inches, also swinging upon pivots. To use this apparatus I proceed thus, dispensing altogether with the cylinders and stirring-rods :-I provide two stoppered flasks, each holding about 200 c.c., and marked respectively A and B. Into flask A I deliver a measured quantity, say 100 c.c. of the distillate (containing an unknown quantity of ammonia), add a proper quantity of Nessler test and shake. A trial solution, made by diluting a known number of c.c. of "standard" ammonia with pure water to exactly 100 c.c. also, is next introduced in flask B, Nessler added, and the mixture shaken. The apparatus, with the tubes in a vertical formula introduced into flask B, tested with Nessler, shaken, and tube B filled therewith as before. The discs of colour will now be found to agree very closely; so much so as to render a third operation needless, except in very precise investigations, when another adjustment can be made as before, and the new formula so obtained used for a fresh assay. The whole operation, after a little practice, will be found shorter and more certain than when cylinders are used, and is capable of a higher degree of accuracy. A few words respecting the precautions to be observed when using the Nessler test may not be out of place. The quantity of "test" employed should be uniform. It should always be added last. No subsequent dilution of such mixtures with pure water should be allowed. Hence a liquid suspected to contain a comparatively large amount ammonia should be diluted to a known bulk previously NEWS and a measured portion taken for testing. Solutions of too deep a colour are not so well compared as those of lighter tint: hence a limit to the length of the tubes employed, and which I do not think could be increased with advantage. A very important question remains-How long after testing should the liquids "stand" before comparing colours? Messrs. Wanklyn and Chapman's invaluable little work upon "Water Analysis" recommends ten minutes. I do not find this time anything like sufficient; true, the distilled liquid containing NH3 in the free state very soon comes up to full tint of colour after testing. Not so the trial mixture; very numerous experiments upon this point have convinced me that this latter is often half-an-hour, or little less in attaining its maximum of colour, and, therefore, comparisons drawn before this occurs would lead to too high results. I attribute this difference of time to the fact that the ammonia in the latter case exists as sulphate or hydrochlorate; and, moreover, in so dilute a state that even the large quantity of free alkali in the Nessler test does not liberate it fast enough. I have sought to remedy this when making a stock of "standard" chloride of ammonium by adding a portion of free KHO just before making up to exact measure, with, however, but partial success. As the problem for solution is the estimation of the ammonia which really quits the surface of the liquid in the retort used in the distillation, rather than that (however slight the loss) which ultimately reaches the receiving flask after condensation, it is a question whether the standard solution should not undergo the same ordeal by being distilled with alkali up to its exact original measure, and then counted to have lost nothing of its strength in the process. Trial solutions made with this latter would then contain NH3 in the same state as it exists in that with which they are to be compared, and when tested would react as quickly with Nessler. Canterbury, April 30, 1873. ON THE CONDENSED EFFLUVE OF THE INDUCTION DISCHARGE.* By M. Th. Du MONCEL. THE attention of chemists having lately been attracted to the effects produced by the condensed effluve of the induction discharge, I have thought it might be useful to communicate some facts connected with this physical phenomenon; the more so that some persons seem to confound the effects in question with those from the spark itself. The electrical phenomenon to which I have given the above name is a sort of luminous discharge produced between two plates of glass, when these plates constitute together the insulating part of a condenser, the armatures of which are connected with the poles of a Rhumkorff apparatus. Thus, let one plate of window glass be separated from another by an interval of 2 or 3 millimetres; apply to their exteriors sheets of tin, or layers of liquid connected with the poles of the induced current, and you will obtain between the two insulating surfaces the electric effluve, which appears in the dark like a luminous rain, of bluish colour, and gives off ozone. To obtain the phenomenon distinctly, the layer of air should be thoroughly dry; otherwise the discharge, instead of furnishing a homogeneous effluve, is concentrated in a small number of sparks of violet colour, which have not the properties of the effluve, properly so called; one of the most important of these being, that the discharge is finely divided over a large surface, and does not produce a heating effect nor sudden mechanical and dis | aggregating action. In virtue of this property one may * Abstract from Comptes Rendus. electrise a gaseous body throughout its entire mass, avoiding the complex reactions which arise from the calorific and mechanical effects of the spark. And as the discharge takes place between two unattackable surfaces, we may obtain electrochemical reaction without oxidations or volatilisations, or accidental absorptions capable of altering the nature of the products. By employing liquid layers as armatures, it is even possible (as M. Thenard has done) to follow by sight the effects successively produced. At the time that I first made known to physicists this curious property of the induction discharge, of traversing glass without breaking it or illuminating the interior, some surprise may have been excited at such an electrical manifestation. But now that the numerous researches in England on the electric condensation produced in submarine cables have cleared up the question of electrical transmission through various bodies, there is no longer cause for this surprise. The phenomenon is explained by conceiving that, under the influence of condensation, the molecules of the insulating body become polarised after the manner of liquid molecules in electrolysis; so that they all conduce, individually and separately, to conducting the discharge from one surface to another of the glass plates. This is what the English have called electrification, and it is complicated by a momentary absorption of part of the charge; this absorption varying with the electrostatic capacity of the insulator. This subject is already well known, and I will only say here that it results from the mode of electrical transmission, and the insulating nature of the surfaces thus electrised, that the electrical charges not being capable of displacement from one point to another to take at the moment of discharge the path of least resistance, as in the case of metallic surfaces, the discharge cannot be concentrated in lines of air, but is forced to continue divided, except in the case in which the air-layer between the insulating surfaces is humid, when, these surfaces becoming conductive, the experiment is similarly conditioned to that of a discharge between two metallic surfaces. The condensed effluve of induction may, in certain circumstances, present the curious aspect of stratified light (so well marked when the induction spark passes in vacuo). To obtain this, one of the plates should be slightly inclined upon the other, forming an acute angle. If one of the armatures is formed by a water-layer, kept in position by a border of mastic, the stratifications may be distinctly perceived; and they are made to disappear when the plates are restored to the parallel position. These stratifications are also observed when the space occupied by the effluve is broad and free of air. relative dimensions of the armatures and their polarity. The intensity of the electric effluve depends on the It is a maximum when the smaller of the two armatures is positive. There is then seen about this armature a beautiful luminous radiation, and if the armature is cut so as to represent a silhouette, it stands out as a Chinese shadow on a luminous ground. I will not dwell on the physical effects of the effluve, as these have been described at length in my notice on the Rhumkorff apparatus; but will simply point out that from an electro-chemical point of view, it may result from the difference of temperature between the effluve and the spark, that under certain conditions the one will act in the opposite direction to the other. Thus, from M. Jean's experiments, it seems demonstrated that ozone is only produced easily in atmospheric air at a low temperature, while at a high temperature the electrisation of the air causes the combination of its two constituent elements, a fact put beyond doubt by the experiments of M. Ed. Becquerel. It results, that according as we cause the effluve or the spark to act on an enclosed layer of air, we obtain ozone or hyponitric acid; and, in certain conditions, this composition. In the case of the spark traversing enclosed difference of action may produce a combination or a deair, as in M. Becquerel's experiment, a combination is |