60 Afialj/s€s of Books. [J Air, 



The product was of a straw colour, evidently containing but very 

 little nitrous acid ; and its specific gravity was 1613, instead of 

 1520, as stated in the Pharmacopceia. It weighed 11*5 parts ; 

 whereas 24 parts of nitre are capable of yielding 17 parts of acid, 

 provided sufficient sulphuric acid is employed to afford water 

 enough to condense the nitric acid. That this is the case is 

 proved by the experiment I am now relating. Sixteen parts of 

 sulphuric acid contain three parts of water ; and it will be seen 

 by Dr. WoUaston's scale that these are sufficient to condense 

 only 8*8 parts of dry nitric acid into 11*8 of nitric acid, of spe- 

 cific gravity 15 ; the difference between actual and theoretical 

 product being only 0-3 of a part, which is as Uttle as can well 

 be expected in experiments of this nature. 



I have already observed that the acid which I obtained has 

 only a straw colour, instead of a red one, as the College seem to 

 expect ; and I believe that whenever the acid has this red 

 colour, it is owing to the presence of common salt in the nitre, 

 the chlorine of which partially decomposes the nitric acid. 



Acidum Nit?icum is directed to be prepared by heating nitrous 

 acid, until the reddish part of it is expelled. If pure nitre be 

 made use of in the first preparation, this operation is totally 

 useless : indeed I am at a loss to imagine any utility in it, even 

 if the acid were as red as the College seem to expect. I have on 

 other occasions remarked, that when the red acid is diluted with 

 water (which it always is before it is used either internally, or as 

 a solvent), that the diluted acid is quite pale. If, however, the 

 College wish for pale nitric acid, it would certainly be better to 

 adopt the London process of using equal weights of nitre and 

 sulphuric acid : this method, although too expensive for common 

 purposes, saves the operation of heating the acid afterwards — 

 an operation attended with some loss, and nearly as much risk 

 as the first preparation of the acid. Added to this, unless the 

 nitric acid be condensed by water, when less than two atoms of 

 sulphuric acid are used to one of nitre, there is a great loss of 

 nitric acid, amounting in the process adopted to about 5-^ parts 

 out of 17. 



Aqua Potass^. — To prepare this, six parts of carbonate of 

 potash are to be rendered caustic by eight parts of lime. The 

 theoretical quantity of lime is only 2^^ parts ; four parts, there- 

 fore, instead of eight would have been more than sufficient. 

 The excess occasions waste by the quantity of solution retained. 



Subcarhonas Ammonice. — One part of muriate of ammonia is 

 directed to be decomposed by two parts of carbonate of hme. 

 The equivalent quantities are nearly 94 of the carbonate to 100 

 of the muriate ; it must, therefore, be admitted that one part 

 and a half would be sufficient instead of two. The excess 

 requires the use of larger vessels and more firing. 



Aqua Ammonia. — In this preparation, the quantity of Hme is 

 uselessly and inconveniently large. Muriate of ammonia it 



