Dr. T. Thomson on Pi/roxylic Spirit and its Compounds. 49 



analogous to muriatic aether, is most conveniently obtained 

 by heating a mixture of two parts of common salt, one part 

 of pyroxylic spirit, and three parts of concentrated sulphuric 

 acid. By the application of a gentle heat, a gas is obtained, 

 which may be collected over water, and which is pure mu- 

 riate of methylene. 



This gas retains its elasticity though cooled down to zero, 

 or even a degree lower. It is colourless, has an aethereal 

 odour, and a sweet taste. It burns with a flame, white in the 

 middle, and green round the edges. Water dissolves 2*8 

 times its bulk of it, at the temperature of 61°, and when the 

 barometer stands at 30 inches. It does not alter vegetable 

 blues, nor does it precipitate nitrate of silver. When deto- 

 nated with an excess of oxygen gas, it is decomposed, and the 

 products are water, carbonic acid, muriatic acid, and some 

 traces of chlorine. The water formed is sufficient to con- 

 dense the muriatic acid disengaged. Each volume of gas re- 

 quires 1- volume of oxygen, and produces a volume of car- 

 bonic acid gas. Hence it is obvious that every volume of the 

 gas contains a volume of carbon vapour, and a volume of 

 hydrogen gas, united into a volume of carbohydrogen. The 

 specific gravity of gaseous chloride of methylene is 1*7310 

 That of carbohydrogen 4861 



1-2449 

 Now, the specific gravity of muriatic acid gas is 1*28472, al- 

 most identical with this residue. Hence there can be no doubt 

 that the chloride of methylene is composed of C H- ChL It 

 is therefore pyroxylic spirit, with an atom of chloride sub- 

 stituted for an atom of oxygen. 



When this gas is made to pass through a red-hot porcelain 

 tube, it undergoes complete decomposition^ being converted 

 into muriatic acid and a carburelted gas, while the porcelain 

 tube is lined with a thin coat of charcoal. The carburetted 

 gas is simple carbohydrogen, for a volume requires for com- 

 plete combustion 1-5 volume oxygen gas, and forms 1 volume 

 of carbonic acid. 



2. Iodide or hydriodate of methylene. — This compound is 

 easily obtained by distilling a mixture of 1 part of phosphorus, 

 8 parts of iodine, and 15 parts of pyroxylic spirit. The 

 iodine is dissolved in the pyroxylic spirit. The solution is 

 put into a retort, and the phosphorus added by little and 

 little. The first fragments added occasion a lively efferves- 

 cence, with the evolution of heat, and the production of hy- 

 driodic acid. When the ebullition thus produced is at an 



Phil. Mag. S. 3. Vol. 15. No. 93. My 1839. E 



