1821.] Mr. Phillips's Reply to Dr. Hope. 23 



2 atoms of sulphuric acid 100*0 



1 atom of potash 59*1 



1 atom of water 1 1-32 



170-42 



I separately powdered, and then mixed, five ounces of acetate 

 of lead with 3 ounces 5-8ths of bisulphate of potash, containing 

 2 ounces l-8th of sulphuric acid, of which one-half, or 1 ounce 

 l-16th, would act upon and expel acetic acid from the acetate 

 of lead ; and it is to be remarked that this exceeds the theoretic 

 quantity requisite, only by about 4 grains. By the heat of a salt- 

 water bath, I obtained in two hours 5-8ths of an ounce of acid, 

 and then removing the retort to the sand heat, there was dis- 

 tilled in less than two hours more, as much acetic acid as made 

 the whole product amount to 2± ounces : it contained rather 

 more than .36' per cent, of real acid, or 1± ounce, being nearly 

 the whole quantity which existed in the acetate of lead. The 

 acetate of lead for this process costs less than bd. ; the bi- 

 sulphate of potash cannot be valued at more than Id. conse- 

 quently at an expense of about old., 1 procure by this pro- 

 cess an ounce of real acid, whereas by your method it costs. 

 I5±d. 



Although I consider, for obvious reasons, that the processes 

 which I have described are all preferable to those in your Phar- 

 macopoeia, there may be yet some objection made to every one 

 of them. Thus although acetate of copper furnishes a compara- 

 tively cheap and really excellent acid, yet it is certainly a costly 

 material. To the use of acetate of lead and bisulphate of potash 

 there are two objections; viz. acetate of lead, always yields an 

 acid which is in some degree empyreumatic, and the oxide of 

 lead forms so insoluble a compound with sulphuric acid, that it is 

 difficult to clean the retort alter the operation. 



All these difficulties are obviated by a process to which t 

 have already alluded, viz. that of decomposing acetate of lead 

 by sulphate of soda, and then treating the acetate of soda formed 

 with sulphuric acid. The results of this method I shall now 

 state. 



Five ounces of acetate of lead were dissolved in water, and de- 

 composed by a solution of 4*3 ounces of sulphate of soda. The 

 solution was evaporated to dryness, the salt reduced to powder, and 

 put into a retort with 1-5 ounce of sulphuric acidand half anounce 

 of water. In three hours and a half, I procured 2% ounces of 

 excellent acetic acid containing 42 per cent, of real acid, or one 

 ounce and one-eighth ; so that the ounce of real acid cost rather 

 less than bd. ; the sulphate of soda is readily washed out of the 

 retort, and is ready to decompose afresh portion of acetateoflead. 

 There is generally a small portion of sulphate of lead diffused 

 through the sulphate of soda, but it is easily washed out with it.. 



