Society of Pharmacy at Paris. 55 



still leaves something to be desired, there remains a final 

 method of remedying it, which consists in filtering through 

 charcoal in powder. The action of this" substance, although 

 little known as to its theory, is nevertheless certain in its 

 effects ; since it is sufficient to boil slightly with it the so- 

 lution of the acetate as above prepared, in order to obtain 

 it perfectly white after filtration and evaporation carefully 

 managed. As to the empyreumatic oil, there is only one 

 wav of avoiding it, which is to stop the distillation of the 

 vinegar at the moment when this principle begins to come 

 over, and the product gives out an empyreumatic smell : 

 for, beyond this term, the vinegar, if still white in appear- 

 ance, would not undergo any change of colour during the 

 evaporation of the acetate; and this colour, when once 

 produced, could not be removed, either by charcoal powder 

 or by any other means whatever. 



The second memoir presents fuller details. Its motto is 

 taken from Boileau : 



" L' artifice agreable 

 Du plus affreux objet fait un objet aimable." , 



The author describes in the first instance the various 

 processes hitherto adopted in preparing the acetate of potash. 

 He mentions as the most exact the process of M. Bouillon 

 Lagrange, which consists in crystallizing this salt ; but he 

 regrets not having been able to put it in practice, from the 

 difficulty of separating the crystallized acetate from the mo- 

 ther waters, which are very thick. In order to obtain as ad- 

 vantageous a result by a more practicable process, he tried 

 double decompositions ; he treated acetate of lime with the 

 carbonate or sulphate of potash, but he did not obtain an 

 acetate of potash less coloured than if he had directly sa- 

 turated the carbonate of potash with distilled vinegar. 



It would be necessary, as he observes, to employ a cry- 

 stallized acetate of lime, but in this case the process would 

 become too tedious and expensive. The decomposition of 

 the common acetate of lead by the carbonate of soda, fur- 

 nished him with a tolerably white acetate of potash : al- 

 though this method unites with the facility of using it the 

 advantage of being cheaper, the author of the memoir does 

 not think it right to resort to it, because the smallest neg- 

 ligence in the operation may change a wholesome medicine 

 into a deadly poison. Recurring to the combination de- 

 scribed of distilled vinegar and potash, he first inquires 

 whence arises the colour assumed by this salt during its 

 evaporation : he is also aware that it is owing to a foreign 

 principle contained in the distilled vinegar; but he after* 



D 4 wards 



