of Edinburgh^ Session 1882-83. 
233 
glycerine in almost the same manner as an alkali, only much less 
powerfully. Chloride of sodium had extremely little action. 
Strong solutions of mineral acids, as hydrochloric and sulphuric 
acids, acted much more slowly than alkalies, and, as was to be 
expected, only a trace of nitrous acid was found amongst the pro- 
ducts of decomposition. Contrary to the experience of De Vrij, 
sulphuretted hydrogen was found to have no action on nitro- 
glycerine when dissolved either in ether or in alcohol. Alkaline 
sulphides, on the other hand, acted very energetically on nitro- 
glycerine, and decomposed it even more powerfully than alkalies. 
The stronger action of the sulphides was especially noticeable when 
a watery and not an alcoholic solution was allowed to act on the 
nitroglycerine. Under this condition an alkali decomposes nitro- 
glycerine very slowly, and only after heating for several hours ; an 
alkaline sulphide decomposes it in almost as many minutes. 
^Nitroglycerine heated for one hour with alcohol alone did not 
exhibit any signs of decomposition ; heated with water for three 
hours it decomposed slowly. 
Some experiments were made to ascertain the highest possible 
practical yield of nitroglycerine from a given quantity of glycerine, 
and the best proportion of acids to obtain this yield. The highest 
yield was over 95 per cent, of the theoretical yield, and this was 
obtained by adding 1 part of glycerine to 9 parts of an acid mix- 
ture, consisting of 2 parts of strong sulphuric acid to 1 part of 
fuming nitric acid. The yield was not improved by substituting 
fuming sulphuric acid for the ordinary strong acid , and the yield 
was greatly lessened when ordinary strong nitric acid was substi- 
tuted for fuming nitric acid. The yield was not to any considerable 
extent increased by allowing the acids to remain in contact with the 
glycerine for a longer period than five minutes. By whatever 
method, or with whatever proportion of acids the nitroglycerine 
was prepared, the products were all found to be uniform in their 
physical and chemical characters. Nitroglycerine does not therefore 
appear to be a body of variable composition as some chemists 
assert (Hess). It is always perfectly colourless, and not yellowish 
as is sometimes stated. The yellow colour is probably for the most 
part due to the nitroglycerine having been washed in the process of 
its manufacture with a solution of soda, which decomposes it. 
