512 Dr. Ure on Pyroxylic Spirit. 



impervious to water. Hats imbued with this varnish exhale 

 in the hot apartments where the process is conducted the va- 

 pours of the wood-spirit very copiously, and thereby occasion 

 a painful irritation to the eyes of the workmen. Some kinds 

 of the spirit are much more injurious to the eyes and the 

 health than others, even when they have all been rectified to 

 apparently the same pitch of purity and strength by the same 

 operations. One purpose of my researches was to discover 

 the causes of these variations, which affect the comfort of the 

 operatives, and another was to discover the causes of the 

 variations in the solvent qualities of wood-spirit of the same 

 strength by the hydrometer. Having hitherto but partially 

 succeeded in the attainment of these two objects, I shall not 

 occupy the time of the Society at present with an account of 

 the experiments made with that view, but shall reserve them 

 for a future communication. 



The researches of Berzelius, Gmelin, Weidmann, Schwei- 

 tzer, Kane, Liebig, Dumas, and Peligot, concur to prove that 

 the ordinary wood-spirit of commerce, even in its most highly 

 rectified state, is not like spirit of wine, merely an alcoholic 

 liquor more or less diluted with water, but that it consists of 

 different compounds mingled together, and very difficultly 

 separable from each other. Wood-spirit, xylite, and mesite, 

 are three of these liquid compounds usually associated in 

 pyroxylic spirit. When the common wood naphtha of the 

 druggist is distilled three or four times from pulverized un- 

 slaked quicklime, by the heat of a water-bath, the oily impu- 

 rities and water are got rid of, and an anhydrous fluid is, 

 obtained which is not liable to become brown on exposure to 

 light, like the ordinary wood naphtha, and which does not 

 become turbid or milky when mixed with water. This puri- 

 fied spirit, however, still acts as painfully almost as the ori- 

 ginal cruder article, upon the eyes of the hatters, as I ascer- 

 tained by trial. One mode of separating wood-spirit from 

 xylite and mesite, is founded upon the property possessed by 

 wood-spirit, of forming a compound with chloride of calcium 

 not decomposable at the heat of boiling water, while similar 

 compounds with xylite and mesite are decomposable at that 

 temperature. I did not find that pyroxylic spirit was essen- 

 tially improved as to its employment in the arts, by being 

 rectified by distillation from its combination with chloride of 

 calcium. 



Methol is the name which has been given to the oil formed 

 by the action of sulphuric acid upon wood-spirit, xylite, and 

 mesite; and I believe the same oil is generated by the simple 

 combustion of pyroxylic spirit ; for I have observed that when 



