4 Drs. Tiedemann and Gmelin in reply to Dr. Prout 



granted, how can Prout's method of determining the free mu- 

 riatic acid in the contents of the stomach be considered as an- 

 swering the object in view ? When free acetic acid, for exam- 

 ple, is present, the potash employed to saturate the free acid 

 will not only saturate the free muriatic acid, but also the free 

 acetic acid. Now as Prout considers his method as quite ac- 

 curate, he must necessarily presuppose the absence of all other 

 free acids. Indeed Dr. Prout would have had reason to com- 

 plain of us, if we had led our readers to believe that he ad- 

 mitted the presence of any other free acid in the liquid of the 

 stomach ; — acetic acid, for example (which is not the case in the 

 paper to which we have alluded). For on such a supposition his 

 method would be no longer accurate ; and we should therefore 

 have placed him in the situation of contradicting himself. 



Dr. Prout, in his remarks upon our treatise, has for the first 

 time, so far as we know, admitted that he has several times 

 found acetic acid along with muriatic acid in the liquid of the 

 stomach. Thus our observations have been confirmed ; and 

 it follows as a consequence, that his method of determining the 

 quantity of free muriatic acid in the stomach cannot be relied 

 upon. That the free acetic acid always proceeds from the food, 

 we cannot believe ; as we have frequently obtained it by the di- 

 stillation of the liquid in the stomach of animals which had 

 long fasted, and whose gizzards had been stimulated by the 

 swallowing of stones, &c. 



2. We have in our account of Proufs method passed by the 

 most important point of the whole, because it constituted a check 

 upon the rest of the procedure. 



Undoubtedly the determination of the muriatic acid in the 

 sublimed sal ammoniac, obtained after the saturation of the 

 liquid of the stomach with potash, is very important ; and it 

 constitutes a still more important check, when one denies (as 

 Prout evidently did in his first paper) the presence of any 

 other free acid in the liquid of the stomach. But as we had 

 discovered the presence of several volatile acids, particularly, 

 of acetic acid, we could not estimate this check as of the least 

 value. For when the liquid of the stomach, together with mu- 

 riate of soda (and potash), contains muriate of ammonia and 

 free muriatic and acetic acids, and we neutralize it exactly 

 with potash, evaporate it to dryness and sublime, the acetate 

 of potash and sal ammoniac which it contains mutually de- 

 compose each other, and are converted into chloride of po- 

 tassium and acetate of ammonia. So that in consequence of 

 the presence of acetic acid, less sal ammoniac will sublime than 

 the liquid of the stomach originally contained. Indeed none 

 at all will sublime, if the quantity of acetic acid be sufficiently 



great. 



