ON PYROXYLIC SPIRIT, &c. m 



obtained a new inflammable gas, which, after freeing it from nitrous and azotic 

 gases with which it was mixed, he inferred from his experiments to consist of 

 1 vol. carbon vapour j- 1 vol. hydrogen + li vol. chlorine ; and to be a sesqui- 

 chloride of the new carbo-hydrogen.* Although Dr Thomson, thus distinctly 

 pointed out the existence of this carbo-hydrogen, he did not positively state 

 that it existed in pyi-oxylic spu-it, which indeed coiUd hardly have been done at 

 the time, as the existing analysis of the latter substance by Macaire and Marcet 

 was inaccurate ; but stiU he appeal's to have had some such idea in view.f 



It is however undoubtedly to MM. Dumas and Peligot, that we are indebted 

 for an accm-ate view of the natm-e and constitution of this liquid, and for the full 

 development of the higlily interesting series of relative substances. Amidst the 

 multitude of detached and isolated facts, which organic chemistry at present of- 

 fers, presenting little interest from analogies, or often supported by merely imagi- 

 nary ones, the development of the pyi-oxyhc series, by unfolding a beautiful ana- 

 logy with alcohol and the ethers, possesses with some other examples, a high de- 

 gree of importance. 



It was to be expected that a similar connection should be observed between 

 pyroxylic spirit and alcohol, in their galvanic relations as in their composition 

 and general properties ; and experiment frilly estabhshed this farther analogy. 



The pyroxyhc spirit employed, was obtained from Glasgow, and for a com- 

 mercial article possessed a high degree of pm-ity. Its coloiu- had a slight yellow 

 tinge. Its specific gravity and boiling point, (taken after it had been a year in my 

 possession) were, the former .851 at 62° F., the latter, in contact with merciu-y, 

 160° F., under 30 inches of pressure. Treated with slaked lime there was no evo- 

 lution of ammonia either in the cold or by heat. By a single distillation from 

 powdered quicklime, it became quite colourless and transparent. After a second 

 distillation from quicklime, its specific gravity was .808 at 62° F. A third dis- 

 tillation from recently ignited and powdered lune brought it dowTi to .801 at 62° 

 F. Its boiling point in contact with mercm-y was then found to be 148°, under 

 a pressm-e of 29.5 inches. | It was with the product of this last distillation, that 

 the galvanic experiments were made. 



* Transactions of the Royal Society of Edinburgh, vol. xi. p. 15. 



f See Inorganic Chemistry, vol. ii. p. 295. 



X The specific gravity of absolute Pyroxylic spirit is given by MM. Dumas and Peligot as .798 

 at 68° F., and its boiling point 151.7° F. at 30 inches of the barometer. In the case of alcohol, the dif- 

 ference of temperature at which the specific gravity was taken by the French chemists and myself, 

 would very nearly account for the difference of specific gravity, and I did not conceive it of any mo- 

 ment to attempt to rectify the pyroxylic spirit more highly, because in regard to alcohol I had found 

 that far greater differences in the density had no material influence on the voltaic results ; and the ana- 

 logy of the action on the two fluids was complete, as will soon appear. 



