It was not until Nobel conceived the idea (in 1866) of absorbing the liquid in some absorbent earth, and thus forming the material that is now known as dynamite, that the use of nitro-glycerine as an explosive became general. Among those who improved the manufacture of nitro-glycerine was Mowbray, who, by using pure glycerine and nitric acid free from nitrous acid, made very great advances in the manufacture. Mowbray was probably the first to use compressed air for the purpose of keeping the liquids well agitated during the process of nitration, which he conducted in earthenware pots, each containing a charge of 17 lbs. of the mixed acids and 2 lbs. of glycerol. A few years later (1872), MM. Boutnny and Faucher, of Vonges,[A] proposed to prepare nitro-glycerine by mixing the sulphuric acid with the glycerine, thus forming a sulpho-glyceric acid, which was afterwards mixed with a mixture of nitric and sulphuric acids. They claimed for this method of procedure that the final temperature is much lower. The two mixtures are mixed in the proportions--Glycerine, 100; nitric acid, 280; and sulphuric acid, 600. They state that the rise of temperature upon mixing is limited from 10 deg. to 15 deg. C.; but this method requires a period of twenty-four hours to complete the nitration, which, considering the danger of keeping the nitro-glycerine in contact with the mixed acids for so long, probably more than compensates for the somewhat doubtful advantage of being able to perform the nitration at such a low temperature. The Boutnny process was in operation for some time at Pembrey Burrows in Wales, but after a serious explosion the process was abandoned. [Footnote A: _Comptes Rendus_, 75; and Desortiaux, "Traite sur la Poudre," 684-686.] Nitro-glycerine is now generally made by adding the glycerine to a mixture of sulphuric and nitric acids. The sulphuric acid, however, takes no part in the reaction, but is absolutely necessary to combine with the water that is formed by the decomposition, and thus to keep up the strength of the nitric acid, otherwise lower nitrates of glycerine would be formed that are soluble in water, and which would be lost in the subsequent process of washing to which the nitro-compound is subjected, in order to remove the excess of acids, the retention of which in the nitro-glycerol is very dangerous. Nitro-glycerol, which was formerly considered to be a nitro-substitution compound of glycerol, was thought to be formed thus-- C_{3}H_{8}O_{3} + 3HNO_{3} = C{3}H_{5}(NO_{2})_{3}O_{3} + 3H_{2}O; but more recent researches rather point to its being regarded as a nitric ether of glycerol, or glycerine, and to its being formed thus-- C_{3}H_{8}O_{3} + 3 HNO_{3} = C{3}H_{5}(NO_{3})_{3} + 3H_{2}O. 92 227 |OH The formula of glycerine is C_{3}H_{8}O_{8}, or C_{3}H_{5}|OH |OH