80 DR MATTHEW HAY ON THE 



might have been decomposed into nitric acid and nitric oxide, or evaporated 

 off'. This form of control-analysis is the more necessary when the salt or 

 substance employed to act on the nitroglycerine is neutral ; and in such 

 circumstances I have always made use of it. 



Phosphate of soda appears, therefore, to act on nitroglycerine in much the same 

 manner as alkalies and alkaline carbonates, only very much less powerfully. 



x I ction of Chloride of Sodium. — Excess of a concentrated solution of the pure 

 salt was mixed with a one per cent, alcoholic solution of nitroglycerine. The 

 salt was not precipitated, as the alcohol contained a little water. The mixture 

 was heated for thirty -five minutes. There was no perceptible change of colour, 

 and the quantity of nitrous acid did not amount to more than a fraction of a 

 per cent, of the nitroglycerine used. The starch reagent yielded no blue 

 colour with the fluid until sulphurie acid was added. The trace of nitrous acid 

 Mas therefore present as a nitrite. One half of the fluid was treated with 

 potash, and from it was procured an amount of nitrous anhydride correspond- 

 ing to 3525 per cent, of the nitroglycerine. The chloride of sodium had not, 

 therefore, decomposed the nitroglycerine and lost the nitrous acid by 

 decomposition or evaporation. 



Chloride of sodium possesses, therefore, extremely little action on nitro- 

 glycerine. 



Action of Hydrochloric Acid. — 1*6 c.c. of the strong acid were diluted with 

 2 c.c. of water and added to 10 c.c. of a one per cent, alcoholic solution of 

 nitroglycerine ; and the mixture was heated over the water-bath for half an 

 hour. It was then found to contain a trace of nitrous acid, not exceeding a 

 small fraction of a per cent, of the nitroglycerine. One half of the fluid, 

 heated with excess of caustic potash, and thus completely decomposed, yielded 

 nitrous anhydride corresponding to 13 5 per cent, of the nitroglycerine. 

 This showed that the hydrochloric acid had decomposed about 39 .per cent, 

 of the nitroglycerine, but whether with the formation of nitrous acid, it is 

 quite impossible to say. For even had nitrous acid been formed, it would have 

 been driven off by the boiling, or decomposed in contact with the water of 

 the fluid. 



Hydrochloric acid, therefore, in large excess, decomposes nitroglycerine 

 much more slowly than a caustic alkali or even an alkaline carbonate, and not 

 much more quickly than phosphate of soda. 



Art ion of Sulphuric Acid. — 0*5 c.c. of strong sulphuric acid was diluted 

 with 1 c.c. of water, and mixed with 10 c.c. of a one per cent, solution of 

 nitroglycerine, and heated for half an hour. At the end of this period the 

 fluid did not contain more than the merest trace of nitrous acid. One half 

 of the fluid, boiled with potash, yielded nitrous anhydride corresponding to 

 297 per cent, of the nitroglycerine. The sulphuric acid had, accordingly, 

 decomposed 11*3 per cent, of the nitroglycerine employed. 



