IntelUsence and Miscellaneous Articles. 315 



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By treating nitrate of silver with perfectly dry chlorine, M. De- 

 ville has succeeded in isolating anhydrous nitric acid, the existence 

 of which was demonstrated by numerous analyses. This beautiful 

 substance is obtained in colourless crystals, which are perfectly bril- 

 liant and limpid, and may be procured of considerable size ; when 

 they are slowly deposited in a current of gas rendered very cold, 

 their edges are a centimetre in length. These crystals are prisms 

 of six faces, which appear to be derived from a right prism with a 

 rhombic base. They melt at a temperature not much exceeding 

 85°*5 F.; their boiling-point is about 113°; at 50° the tension of 

 this substance is very considerable. In contact with water it becomes 

 very hot, and dissolves in it without imparting colour, and without 

 disengaging any gas ; it then produces with barytes the nitrate of 

 that base. When heated its decomposition appears to commence 

 nearly at its boiling-point ; this circumstance is an obstacle to the 

 determination of the density of its vapour by the process of M.Dumas. 



The process by which M . Deville obtained anhydrous nitric acid 

 is very simple ; but the readiness with which it penetrates tubes of 

 caoutchouc renders it necessary to unite all the pieces of the appa- 

 ratus by melting them. The following is the process : — the author 

 employs a U-shaped tube capable of containing 500 grs. of nitrate 

 of silver, dried in the apparatus at 356° F. in a current of dry car- 

 bonic acid gas. Another very large U-tube is connected with this, 

 and to its lower part is attached a small spherical reservoir ; it is in 

 this reservoir that a liquid is deposited which always forms during 

 the operation, and which is excessively volatile (nitrous acid ?). The 

 tube containing the nitrate of silver is immersed in water covered 

 with a thin stratum of oil, and heated by means of a spirit-lamp 

 communicating with a reservoir at a constant level. The chlorine 

 issues from a glass gasometer, and its displacement is effected by a 

 slow and cons^tant flow of concentrated sulphuric acid. The chlorine 

 must afterwards pass over chloride of lime, and then over pumice- 

 stone moistened with sulphuric acid. At common temperatures no 

 effect appears to be produced. The nitrate of silver must be heated 

 to 203° F., the temperature being then quickly reduced to 136° or 

 154°, but not lower. At the commencement, hyponitrous acid, di- 

 stinguishable by its colour and ready condensation, is produced ; and 

 when the temperature has reached its lowest point, the production 

 of crystals begins, and they soon choke the receiver cooled to 6° 

 below zero ; they are always deposited upon that part of the receiver 

 which is not immersed in the freezing mixture, and M. Deville states 

 that ice alone is sufficient to occasion their formation. 



The gases are coloured, and the small sphere of the cooled tube 

 contains a small quantity of liquid, which must be taken from the 

 apparatus before the nitric acid is removed to another vessel ; this 

 latter operation is readily effected by replacing the current of chlorine 

 by one of carbonic acid. The condenser is then to be no longer 

 cooled, and the vessel for receiving the crystals is to be immersed in 

 a freezing mixture ; this is fastened to the producing apparatus by 

 means of a caoutchouc tube furnished with amianthus. The chlo-^ 



