COMPOUND ANIMAL SUBSTANCES. 99 



the remaining portion of those two constitnents. Other sulj- 

 stances are contained in the spirituous sokition, wliich may be 

 distinguished and separated by the rules already given. 



The residue not taken up by the alcohol of -915 must be 

 treated for some time with water, by which pyin, ptyalin, and 

 water-extract will be taken up. The albumen remains as a 

 residue, usually more or less reddened by a little h^ematin. 



If the fluid be very rich in albumen, this course does not 

 succeed, inasmuch as we are unable to obtain a complete sepa- 

 tion of those substances Avhich are soluble in dilute alcohol, as 

 sugar, urea, salts, and extractive matters. The following simple 

 modification may in that case be adopted. The protein-com- 

 pounds must be precipitated by anhydrous alcohol. A spiritu- 

 ous solution is thus obtained, which, even when concentrated, 

 holds the m'ca, sugar, &c., in solution, while the protein-com- 

 pounds (at least the albumen) are reduced to an insoluble con- 

 dition. The coagulated protein-compounds are always mixed 

 up with a certain amount of foreign matters, as, for instance, 

 water-extract, which cannot be easily separated. After the 

 removal of the albumen, &c., the spirituous solution must be 

 evaporated to the consistence of a syrup. On the addition of 

 anhydi'ous alcohol, sugar, spirit-extract, any albumen that had 

 escaped the former process, and some other substances, will be 

 precipitated. The alcoholic solution must be evaporated, and 

 the residue dissolved in water, by which means the fat will se- 

 parate itself. The fat is, however, difficult to remove, in con- 

 sequence of the slow and torpid manner in which the fluid 

 permeates the filter. It is better, therefore, to evaporate the 

 alcoholic solution, at a very gentle temperature, to dryness, and 

 then to take up the fat with pm'e ether. 



In searching for minute quantities of urea in alcoholic solu- 

 tions of concentrated animal fluids, it frequently happens that, 

 after evaporation of the alcohol, the removal of the fat, and the 

 solution of the residue in water, the action of nitric acid on the 

 urea is much impeded by the presence of compounds of the 

 fatty acids. I therefore usually remove the bases from the 

 alcoholic solution by means of sulphm*ic acid, which liberates 

 the fatty acids, and allows of their removal with the fat by 

 means of ether. The sulphuric acid should be much diluted 

 with strong alcohol; and as it is of importance that there 



