408 Dr, Prout on Digestion [Dec. 



fixed alkali as determined above, and subtracting the sumifrom 

 the total quantity of muriatic acid present, the pro porttotiii^ acid 

 in union with ammonia was estimated. But as u t;/teck )to this 

 result, the third neutralized portion above-mentiomd vf<ts ^rnapo* 

 rated to dri/nesi,andthe muriate of ammonia expelled by heat^ and 

 collected. The quantify of muriatic acid, this coniairieilwa^ then 

 determined as before, and was always found to represent neurly 

 the quantity of muriate of ammonia as before estimated^ llius 

 proving the general accuracy of the whole experimentsi.b^j^nd a 

 doubt, 4. The remaining fourth portion of the original fluid 

 was reserved for miscellaneous experiments." Now> in their 

 account of my method, MM. Tiedeman and Gmelin havetxDtally 

 omitted the part in italics, without which, when ammonia is 

 present (but not otherwise), the process would be unsatisfactory, 

 as I well knew, but which entirely removed the only objection 

 that could be made to it. I may also here mention that there 

 tvas another circumstance which operated as a check to my 

 Results, and which, by some accident, was omitted in my paper, 

 viz. that the third neutralized portion above-mentioned ;•e^^fl2we(/ 

 7ieutral after combustion, which could not have been the case 

 liad the free acid present been of a combustible nature. This 

 ■was a point always particularly attended to ; and on reference to 

 my notes, I find that, at the time my paper was written, tio 

 instance of the contrary had occurred to me. Since that time, 

 however, as has been already mentioned, I have met with a few 

 instances of the presence of combustible acids in the stomachs 

 of animals. And here, perhaps, it may not be amiss to make a 

 few remarks on the method in question, which seems in general 

 not to have been duly appreciated by chemists. The mere deter- 

 mination of the existence of a principle in any compound, with- 

 out its quantity be at the same time ascertained, is often unsatis- 

 factory ; at least the determination of the latter point 

 corroborates the former in no small degree ; for before the quan- 

 rtiXy of a substance can be ascertained, it must be obtained />cr«e, 

 ojin some well-determined state of combination, circumstances 

 jiecessarily implying a much more complete and satisfactory 

 investigation than that by mere tests only. My object, there- 

 fore, was to contrive a method, by which both these points 

 might be determined with precision at the same time. After 

 trymg a great variety, (for those related are by no means to be 

 considered as the only experiments made on the subject) the 

 one above mentioned was chosen as the best suited to my pur- 

 pose; and so completely did it seem to answer the end in 

 view, that had i detailed all that was done besides, which 

 •would have half filled the volume of the Transactions, 1 do 

 not thiBk that the point in question would have been a whit 

 better establislied. 1 may, however, mention here, that among 

 other means, distillation, as subsequently employed by Mr. 



