NITRO-MURIATIC ACID 423 



amounts to 1 84 grms. of pure nitro-glycerine. According to Railton, mtro-glycerine 

 is decomposed by evaporation even in vacua over sulphuric acid at ordinary tem- 

 peratures. 



2. Half an ounce of dehydrated glycerine is poured, with constant stirring, into a 

 mixture of 2 ozs. of oil of vitriol and 1 oz. fuming nitric acid of specific gravity 1'52, 

 the temperature of the mixture being kept below 25 Cent, by external cooling with 

 ice ; and as soon as oily drops begin to form on the surface, the mixture is poured, 

 with constant stirring into 50 ozs. of cold water. Nitro-glycerine then separates, 

 and may be purified by washing and drying, in small portions, in a vapour-bath. 



According to Gladstone, nitro-glycerine exhibits different properties according to the 

 manner in which it is prepared. Ordinary hydrated glycerine, added to a mixture of 

 3 pts. sulphuric and 1 pt. fuming nitric acid, is converted into a liquid which detonated 

 violently under the hammer; but anhydrous glycerine treated in like manner, yields a 

 non-explosive body which burns without noise. Both kinds of nitro-glycerine when 

 exposed to a mixture of solid carbonic acid and alcohol become gummy, and assume 

 the appearance of fatty acids ; and both decompose spontaneously with evolution of 

 red vapours. A sample of nitro-glycerine, which decomposed in this manner on expo- 

 sure to summer sunshine, yielded crystals of oxalic acid, together with two liquids, the 

 upper of which contained nitric acid, ammonia, oxalic acid, hydrocyanic acid, and 

 other compounds not examined. Mills found that nitro-glycerine kept a fortnight, no 

 longer exploded when struck, but showed no signs of decomposition or chemical 

 alteration. 



Nitro-glycerine is well adapted for blasting, its destructive action being estimated at 

 about ten times that of an equal weight of gunpowder. The first attempts to apply 

 it as a mining agent were by A. Nobel, a Swedish engineer, in 1864. Some experi- 

 ments were first made with gunpowder saturated with nitro-glycerine. This powder 

 burnt much as usual in the open air, but when confined in shells or blast-holes it 

 produced greater destructive effects than ordinary gunpowder. Nitro-glycerine cannot 

 be employed as a blasting agent in the ordinary way, as the application of a flame 

 from a cannon-fuse would not cause it to explode ; but when it is introduced in a 

 suitable case into a blast-hole, and a fuse having a small charge of gunpowder 

 attached to its extremity is fixed immediately above it, the concussion produced by 

 the exploding gunpowder effects the explosion of nitro-glycerine. The use of nitro- 

 glycerine is, however, attended with very great danger, on account of its great liability 

 to explode by concussion or by friction during transport. Moreover, it solidifies at a 

 temperature probably as high as 8 C. (56 Fahr.), and the friction of the frozen par- 

 ticles is very apt to give rise to explosion. Nobel has, however, found that the danger of 

 accidental explosion of nitro-glycerine may be obviated by mixing it with wood- spirit, 

 which renders it non-explosive by percussion or by heat. "When required for use, it 

 may be recovered by adding water to the mixture, which precipitates the nitro-glycerine. 

 See EXPLOSIVB COMPOUNDS. 



IfflTRO-NIURIATIC ACZB, or Aqua regia (Acidenitro-muriatigue, Fr. ; Salpe- 

 tersalzsdure, Konigswasser, Ger.), is the compound menstruum invented by the alche- 

 mists for dissolving gold. If strong nitric acid, orange-coloured by saturation with 

 nitrous or hyponitric acid, be mixed with the strongest liquid hydrochloric acid, no 

 other effect is produced than might be expected from the action of nitrous acid of the 

 same strength upon an equal quantity of water ; nor has the mixed acid so formed 

 any power of acting upon gold or platinum. But if colourless concentrated nitric 

 acid and ordinary hydrochloric acid be mixed together, the mixture immediately 

 becomes yellow, and acquires the power of dissolving these two noble metals. Mr. E. 

 Davy seems first to have obtained a gaseous compound of chlorine and binoxide of 

 nitrogen in 1830, and a combination of these two constituents was distilled from aqua 

 rcgia, and liquefied by M. Baudrimont in 1843. But it was not until M. Gay-Lussac 

 investigated the subject (Annales de Chimie, 3me ser. xxiii. 203 ; or Chemical Gazette, 

 1848, p. 269) that the true nature of the mutual action of nitric and hydrochloric 

 acids was fully explained. When these two acids are mixed in a concentrated state, 

 a reaction soon commences, the liquid becomes red, and effervescence takes place, 

 from the escape of chlorine and a chloro-nitric vapour. On passing this gaseous mix- 

 ture through a U-tube, the bent part of which is immersed in a freezing mixture of 

 ice and salt, the chloro-nitric compound is condensed as a dark-coloured liquid, and 

 is thus separated from the chlorine which accompanied it. 



Chloro-nitric acid, N0 2 C1 2 (NOC1 2 ), may be represented as a peroxide of nitrogen, 

 in which two equivalents of oxygen are replaced by two equivalents of chlorine. This 

 chloro-nitric acid does not take any part in the dissolving of gold and platinum, which 

 is effected by the chlorine alone. Chloro-nitric acid may also be formed by mixing 

 the two gases, binoxide of nitrogen and chlorine, in equal volumes, which assume a 

 brilliant orange colour, and suffer a condensation of exactly one-third of their original 



