206 RESEARCHES UPON THE CHEMICAL PROPERTIES OF GA.SES. 



weak palladium chloride solution heated nearly to 100°. On spontaneous evapora- 

 tion, the solution deposits monoclinic crystals easily recognized under the micro- 

 scope. If the mercaptan compound appears (cinnamon-colored powder) the solution 

 may be boiled. The methyl sulphide compound then goes into solution. The mer- 

 captan compound is insoluble. On evaporating the filtrate, the methyl sulphide 

 compound crystallizes in monoclinic prisms. If sulphuretted hydrogen and methyl 

 hydrosulj^hide are suspected to occur, these two gases may be completely absorbed 

 by caustic soda. The methyl sulphide is unabsorbed by soda, and by warming the 

 soda solution it may be prevented from condensing upon the surface of the liquid. 

 By using a solution of lead oxide in caustic soda, which absorbs sulphuretted hydro- 

 gen and methyl hydrosulphide, it is possible afterwards to expel the methyl hydro- 

 sulphide by cautious addition of dilute hydrochloric acid, the sulphuretted hydrogen 

 being then held back by the lead as lead sulphide (Klason, loc. cit.). 



Lastly, the terrible odor of the methyl hydrosulphide is sufficient for its identi- 

 fication under all circumstances. 



NITROGEN. 



Although readily prepared by the absorption of oxygen from air by pyrogallol, 

 the resulting nitrogen contains carbon monoxide, as shown by Tacke (^Archw. f. d. 

 Oes. Physiol., XXXVIII, p. 401). Ferrous sulphate in an excess of alkaline citrate 

 solution is unsatisfactory as an absorbent for atmospheric oxygen on account of the 

 extreme slowness of its action. I have found that ferrous chloride mixed with thick 

 milk of lime acts more rapidly for the reason that, on agitating in a glass vessel, the 

 pastry mass coats the walls and better exposure of the precipitated ferrous hydrate 

 to the air is effected. The nitrogen used in the following experiments was prepared 

 as described below. 



Air was shaken with a mixture of pyrogallol and caustic soda solution. The 

 resulting impure nitrogen was caused to pass slowly through a heated combustion 

 tube filled partly with metallic copper (reduced by hydrogen from copper oxide) and 

 partly with copper oxide. 



Ledue (Compt. lievid., V, CXIII, p. 71) has shown that copper used to remove 

 oxygen from air should be made by the reduction of copper oxide at a low tempera- 

 ture, in order to avoid the formation of copper hydride and consequent contamina- 

 tion of the nitrogen by hydrogen. This impurity may, however, be removed by 

 using some copper oxide in the heated tube. It may be stated that in a series of 

 experiments, using pyrogallol and alkali in different proportions and in difterent 

 degrees of concentration, it was not possible to obtain pure nitrogen. In every case 



