''^^''^^' MNitropicric Aciit!^^''^^ * 37 



nitropicric acid, and is therefore by far its most oeconomical 

 source. 



A quantity of nitropicric acid was digested with water and 

 bromine in a retort, so connected with a condensing apparatus 

 that the bromine and acid vapours, on cooling, flowed back into 

 the mixture. As cork was rapidly attacked and destroyed by 

 the bromine vapours, the different parts of the apparatus were 

 connected by means of plaster of Paris. The mixture of bro- 

 mine and nitropicric acid was digested for several hours ; and 

 when the greater portion of the bromine had disappeared, new 

 quantities of it were added from time to time, and the digestion 

 continued. Bromopicrine and bromanil were, with the exception 

 of hydrobromic acid, almost the sole products. Permanent gases 

 were evolved only in comparatively small quantity, their amount 

 increasing towards the close of the digestion. No carbonic acid 

 was evolved, and the gases consisted chiefly of nitrogen and its 

 oxides, especially the binoxide. The production of these gases 

 appears to arise from the decomposition of bromopicrine. It 

 seems, therefore, that nitropicric acid, when it is digested with 

 bromine, is resolved into bromanil and bromopicrine, probably 

 as follows : — 



2(Ci2 H3 (N04)3 02) + 28Br=Ci2Br4 04 + 6(02 61-3 (NO^)) 



+ 6HBr. 



'^p Bromopicrine, C^Br^NO"^. — When the products obtained by 

 the preceding operation are rectified, bromopicrine of a deep 

 yellow colour, from containing excess of bromine, distils over, 

 and forms an oily fluid under the aqueous solution which has 

 come over with it. It was washed with water containing a little 

 carbonate of soda, and then agitated with mercury to remove 

 any adhering bromine. Although the boiling-point of bromo- 

 picrine is much higher than 212° F., it came over chiefly with 

 the first portions of the water, and was perfectly colourless when 

 the excess of bromine had been previously removed. But when 

 bromopicrine had been rendered anhydrous by contact with fused 

 chloride of calcium, though it might be heated to nearly its 

 boiling-point without alteration, yet when it began to boil it was 

 partially decomposed, with the evolution of brownish-red vapours, 

 even though the operation was conducted in an atmosphere of 

 carbonic acid gas. As it was plain therefore that anhydrous 

 bromopicrine could not be purified by distillation, it was sepa- 

 rated from the chloride of calcium by filtration, none of the 

 chloride of calcium being retained in solution. The bromo- 

 picrine prepared in the way just described, when subjected to 

 analysis, gave 85*1, 85-2, and 85*6 per cent, of bromine. The 

 formula of bromopicrine (C'^Br^NO'^) requires only 80*54 per cent. 



