114 Mr. Mill on Acetate of Soda, [Aug: 



of soda, but a compound salt, consisting of sulphate of soda and 

 acetate of soda. The mother water when tested gave precipitates 

 of both sulphate of lime by sulphuric acid and sulphate of 

 barytes by muriate of baiytes, thereby proving that acetate of 

 lime and sulphate of soda are incompatibles only to a certain 

 extent ; for they may and do exist at the same time in the same 

 solution. If acetate of lime be added to the mother liquor 

 ad iufirntum, the sulphate of soda will noi be totally decomposed ; 

 nor, on the contrary, if sulphate of soda be added to the mother 

 water instead of the lime, will the lime which existed in the 

 liquid disappear, for oxalic acid still occasions a copious preci- 

 pitate. 



Crystals procured from either of these last solutions, whether 

 acetate of lime or sulphate of soda be in excess, still give as 

 large a precipitate with muriate of barytes as heretofore, thereby 

 indicating that the sulphate of soda is not wholly decomposed, 

 and that a perfect acetate of soda cannot be obtained through the 

 medium of sulphate of soda. 



I am also of opinion, that most of the acetates are deficient in 

 the power of totally decomposing the sulphates, which opinion 

 is strengthened by Dr. Thomson's experiments to discover the 

 atomic weight of acetic acid. Annals of Philosophy , ii. p. 142, 

 N. S. He found acetate of lead to be nearly in the same situa- 

 tion as acetate of lime ; for he states, that " acetate of lead does 

 not possess the power of throwing down the whole of the sulphu- 

 ric acid from the solution of a sulphate/' If this be the case, 

 the process you have given for procuring acetic acid from the 

 double decomposition of the acetate of lead and sulphate of soda 

 must be defective, inasmuch as this, that the acetic acid is not 

 procured from acetate of soda (which should result from the 

 perfect decomposition) in toto, but from a compound salt of 

 acetate of lead and acetate of soda. In order to ascertain the 

 proportions of sulphate of soda in the crystallized salt before 

 alluded to, I dissolved 100 grains of the crystals in water, and 

 added muriate of barytes so long as any deposition took 

 place, the precipitated sulphate of barytes was then collected, 

 dried, and weighed 10 grains, which is equivalent to 14*7 grains 

 of the crystallized sulphate of soda. This salt is, therefore, 

 composed of (in 100 parts) 



Crystallized acetate of soda .... 85'3 

 Crystallized sulphate of soda. .. 14-7=: 100. 



As the pyrohgneous acid manufacturers commonly decompose 

 acetate of lime by sulphate of soda to procure acetate of soda, 

 it must be of some importance to them to know that, indepen- 

 dently of the loss of the salts left in the mother water by this 

 process, they also procure an impure article. 



Youif obedient servant^ Nicholas Mill, 



