an excess of oxygen and the metal manganese, one part of the muriatic acid is decomposed, its chlorine passes to the pneumatic trough, while its hydrogen seizes a portion of the oxygen from the manganese, to form water. (Vide experiment 32.) Experiment 37.-If we require a small quantity of chlorine quickly, it can be obtained by pouring a spoonful of muriatic acid upon the same quantity of chloride of lime, composed of chlorine and lime; the muriatic acid, by superior affinity, unites with the lime, while the chlorine seeks its liberty; this is not sufficiently pure for some of the following experi ments: Experiment 38.-From the articles on oxygen and hydrogen, it will be seen, that when we burn a taper in common air, the oxygen of the latter is seized by the hydrogen and carbon of the taper, to form water and carbonic acid: if, on the contrary, we suspend a lighted taper in chlorine, it is only its hydrogen that burns, while the carbon passes off, forming a dense black smoke in this operation the hydrogen unites with the chlorine, to form muriatic acid, (vide experiment 36) as it burns it will remind us of the appearance of the sun during a dense fog. : Experiments 36 and 38 illustrate in a very remark. able manner the important operations in chemistry termed analysis and synthesis-the first, (derivation Greek, avuλvw, to loosen,) is resolving a body into its constituent parts. In experiment 36 we found muriatic acid to be composed of chlorine and hydrogen: in experiment 38, a case of synthesis, (derivation E Greek, svvτionμi, to compose,) we formed a compound muriatic acid which we had previously analysed. 48.-When speaking of oxygen, it was stated that it did not invariably form acid, (vide 40,) as Lavoisier supposed experiment 38 forcibly corroborates this statement; the advanced student will find many other instances. : Experiment 39.-It will be important to prove that chlorine affects colours, thus constituting a bleaching agent: suspend some pieces of moistened linen cloth, variously coloured, in chlorine gas, they will be bleached immediately, if they have been dyed with vegetable or animal colours; the object of moistening the cloth is to allow the chlorine to decompose the water, thus forming muriatic acid by abstracting its hydrogen that such an effect is produced is evident, from the fact that dry colours are not affected. : Experiment 40.-Suspend a moistened engraving, stained with ink, in chlorine, the engraving comes out uninjured, while the ink disappears. In consequence of this property of chlorine, it has been employed by dishonest persons for erasing names and sums of money out of wills; this fact should be known to every member of society: a simple preventive is, to use, on such important occasions, indestructible inks; many have been recommended; the following is easily prepared :-mix fine lamp-black with sulphate of indigo (indigo dissolved in sulphuric acid, which can be procured at the dyer's); this mixture is not affected by chlorine. QUESTIONS. 159. Who discovered chlorine ? 160. Why was it so termed ? 161. Is it lighter or heavier than the atmosphere ? 162. Does it support life and combustion? 163. What effect has it on vegetable and animal colours? 164. Why is it called a disinfecting agent? 165. When we mix muriatic acid with black oxide of manganese to form chlorine, what are the proportions? 166. Why is it necessary to use warm water in the pneumatic trough? 167. Is any precaution necessary while we are liberating the gas? 168. Can you explain why chlorine is liberated by the process? 169. When this gas is united with lime, what is the compound termed ? 170. How can we separate the chlorine from the chloride of lime, to use it as a disinfecting agent? 171. You have seen that chlorine partially supports combustion, when the lighted taper was in it what caused the dense smoke? 172. What acid was formed by the union of chlorine and hydrogen? 173. What is the difference between analysis and synthesis? 174. When we suspend coloured cloth in chlorine to bleach it, why is it essential that it should be moistened? 175. As common ink is removed by this gas, what should be used for writing wills, &c. 176. Describe the experiment with muriate of tin, to illustrate the use of mordants in dyeing. 177. Are thin metallic leaves affected by chlorine? 178. How can we form chlorine water? |