

Chemical Science, 403 



ployed; and it accordingly is evident that the bisulphate and the 

 nitrate commence only to act on each other at that temperature.. On 

 increasing the heat, the retort becomes filled with red vapours ; 

 oxygen is evolved and nitrous acid distils over, and is dissolved by 

 the aqueous nitric acid in the receiver. The emission of red vapours 

 continues when the retort is red hot, and it appears, consequently, 

 that even at so high a temperature a large quantity of the nitrate ia 

 left undecomposed by the bisulphate. 



If the quantity of sulphuric acid employed be just sufficient to pro- 

 duce the sulphate, the temperature required for the distillation of the 

 acid does not exceed 302 F. ; after half the quantity of the acid in 

 the nitrate has been distilled over, the residue consists of bisulphate. 

 and nitrate of potash, which, on increasing the temperature, act 

 on each other in the manner above described viz., oxygen and 

 nitrous vapours are evolved, and the liquid in the receiver is coloured 

 by nitrous acid. The quantity of water employed in the process is 

 quite indifferent, and influences only the strength of the distilled 

 acid, which, previous to increasing the heat above 302 R, is perfectly 

 colourless. According to this process, that is to say, where the quan- 

 tity of sulphuric acid is 48.41 to 100 of the nitrate, the quantity of 

 nitric acid produced does not exceed six- sevenths of that previously 

 contained in the nitrate. 



Nearly the same result is obtained by distilling 100 parts of nitre 

 with 72.6 of sulphuric acid ; but in this, as well as in the last process, 

 a very great heat is required to decompose the last proportions of nitre, 

 part of the acid of which will, moreover, also be found to be lost. 

 But if, with 100 parts of nitre, 96.8 parts of acid are used, so that 

 the bisulphate of potash is formed, the process will be found to be 

 far more profitable, for none of the acid is lost : distillation takes 

 place very easily, and at a heat not exceeding 248 to 257 F. ; the 

 nitric acid obtained is of 1.512 gravity, which, by distillation, may 

 be increased to 1.54. The- former, which is colourless, contains 

 86.17; the latter is rather yellowish, and holds 88.82 per cent, of acid. 



If water is added to the acid of 1.522, the boiling point of the 

 liquid gradually rises ; and, on distillation, first concentrated and 

 then weak acid will be found to pass over. This continues, however, 

 only until the quantity of water amounts to 44 per cent, of the acid, 

 the specific gravity of which is then 1.40, and the boiling degree be- 

 tween 248 and 249 F. ; if the quantity of water is still increased, 

 the boiling point falls, and the order of the distillation is, as it were, 

 contrary to what it was observed before viz., first weak and then 

 strong acid is obtained. This likewise takes place during the distil- 

 lation of nitric acid from nitre ; for if, with 100 parts of nitre and 

 96.8 of sulphuric acid, the quantity of water is not equal to 44 per 

 cent, of the acid formed, the first produce of distillation is strong, 

 and the next diluted acid ; if more water is employed, the contrary 

 takes place. 



It is, accordingly, most advantageous to use 100 parts of nitre, 96.8 

 of sulphuric acid, and about 40.45 of water, which will be sufficient, as 



