30 Mr. Phillips's Reply to Dr. Hope. [July, 



decomposed ; for 10 parts of sulphuric acid contain 8' 15 of dry 

 acid, and 10 parts of salt yield 5-35 soda; the weight of the resi- 

 duum should, therefore, have amounted to 13*5 parts. 



Operating in the same manner, I used, according to the scale, 

 the equivalent quantities of sulphuric acid and common sait ; 

 viz. 8*4 of the former, and 10 of the latter, the cost being 1*68 

 for the sulphuric acid, and 4 for the salt, amounting to 5*68. 

 On examining the residuum, I found that 1'7 part of the salt 

 remained undecomposed, showing that the expense of decom- 

 posing 8*3 parts of it amounted to 5*68 ; whereas by your pro- 

 cess it is rather less than 5 ; for 10 : 6 :: 8*3 : 4-98. 



While, however, I allow the preference that ought to be given 

 to your process, 1 cannot admit the justness of the reasoning 

 upon which you found its superiority. You observe that it 

 must " for the moment have escaped my recollection, that 

 sulphuric acid is much disposed to form a supersulphate of 

 soda, and consequently that if no more acid be employed than 

 is barely safhcient to saturate the quantity of soda contained in 

 the muriate, a considerable portion of the muriate will remain 

 undecomposed." Now if the decomposition of the common salt 

 depended upon the formation of bisulphate of soda, as you seem 

 here to hint, you ought to have employed 16*8 of sulphuric acid, 

 instead of only an equal weight, with 10 of common salt. It is, 

 however, quite evident, that the decomposition of the common salt 

 is not dependent upon the formation of a bisulphate ; for not only, 

 as I have just shown by your process, 10 parts of sulphuric acid 

 are capable of effecting what ought to require 16*8 ; but in the 

 other experiment which I have detailed, 8*4 parts of the acid 

 decomposed 8*3 of common salt, which are the quantities requi- 

 site to form common sulphate of soda as nearly as 84 to 10. 



Aqua Potassce. — From repeated experiments on the subject, I 

 am convinced that the quantity of lime which you order is unne- 

 cessarily large ; and that even supposing you obtain, as you 

 assert, the whole of the potash, the method is tedious on account 

 of the long time which it occupies. 



Subcarbonas Ammonite. — On this head also I must retain my 

 former opinion ; for where the equivalent quantities are 100 of 

 muriate of ammonia to 95 of carbonate of lime, I conceive it to 

 be utterly impossible that it can be of any use to employ twice 

 the quantity of the carbonate, as you direct, although I am per- 

 fectly willing to admit, as with respect to the preparation of 

 muriatic acid, that an excess of the cheaper material ought 

 always to be employed. You will find in my examination of the 

 London Pharmacopoeia, in treating of the preparation next to be 

 noticed, that I propose to use a considerably larger quantity of 

 lime than the equivalent. 



Aqua Ammonia?. — The process of the Edinburgh Pharmaco- 

 poeia consists in decomposing 12 parts of muriate of ammonia 

 by means of 18 oflime previously slaked with nine parts of water, 



