acetatis feni. — On this account care should be taken that in 

 drying the mixed salts, according to the processes in the 

 Dublin Pharmacopoeia, the heat should not be increased be- 

 yond the degree there specified. 



The deposition which takes place in the tincture drawn by 

 rectified spirit I supposed might depend on the Iron having 

 attracted oxygen either from the atmosphere or from the 

 water which forms part of the rectified spirit, and thus be- 

 coming less soluble in the acetic acid, and conceived that by 

 exposing the mixture to air, so as to satisfy this attraction, 

 the acid avouM take up such a quantity only of the oxyd as 

 it would afterwards retain in a state of permanent solution. 

 The exposure of the mixed salts to air was accordingly di- 

 rected in the specimen printed in 1794, with the intention of 

 more effectually preventing the decomposition of the Ale. 

 tincture. Repeated experiments have, since that time, con- 

 vinced me, that this precaution is unnecessary,* and even 

 detrimental if the mixture be exposed too long to air, espe- 

 cially in the higher temperatures; the reason of this may 

 be inferred from the experiments above-mentioned, which 

 prove that Iron may be so oxydated as to become almost 

 altogether insoluble in acetic acid. 



Finding that the tincture in rectified spirit grows turb!d in 

 phials stopped so as to exclude the air, I am now inclined to 

 impute the deposition of the oxyd to the reaction of the wa- 

 ter contained in the diluted spirit upon the acetic acid of the 



martial 



* Provided the ;Mcohol be of the specific gravity before meutioned. 



