182 CIRCULATING FLUIDS : 



phosphates and sulphates of lime^ magnesia^ potash, and soda. 

 If they are dissolved in a little dilute nitric acid^ the addition 

 of ammonia induces the precipitation of the earthy phosphates, 

 while the other salts remain in solution. 



There are some substances occurring only in very minute quan- 

 tities, or in certain diseased states, which cannot be always 

 easily detected. 



1. Urea. This substance has never yet been observed in 

 any great quantity in the blood. 



I have detected a minute quantity of urea in the blood of a 

 healthy calf. I allowed the blood (about fifteen or sixteen pounds) 

 to run into a vessel filled with alcohol, and assiduously stirred 

 the mixture. The alcohol was removed by pressure, evaporated, 

 and the residue extracted with anhydrous alcohol. After filtra- 

 tion, and a second evaporation, the residue was again dissolved 

 in a little anhydrous alcohol, and the bases of the lactates and 

 fatty acids precipitated with sulphuric acid. The filtered liquid 

 was digested with carbonate of baryta, evaporated, dissolved in 

 water, the fats and fatty acids removed by filtration, the aqueous 

 solution concentrated, and nitric acid added. The greater part 

 of the fluid was removed by being placed in vacuo over strong 

 sulphuric acid; alcohol was poured over the residue, and the 



cium, there is a copious gelatinous precipitate of phosphate of lime (3CaO, POj), 

 which tlissolves in nitric acid without eflfervescence. On treating this acid solution 

 with nitrate of silver, and neutralizing with ammonia, the tribasic phosphate of silver 

 is precipitated as before. The addition of the chloride of calcium neutralizes the 

 previously alkaline fluid. 



From 1, we see that the alkaline reaction is not due to the presence of alkaline 

 carbonates ; and 2 shows it is not dependent on the presence of free potash or soda, 

 for otherwise the fluid would not be neutraUzed by the chloride of calcium. Hence 

 the albumen in the blood cannot exist as a soda-compound (all)uniinate of soda) ; 

 neither can there be alkaline lactates, acetates, nor fatty-acid salts in that fluid ; and 

 on the above grounds, Enderlin conceives that we are justified in assuming that the 

 alkaline reaction of the ash is dependent on the presence of tribasic phosphate of 

 soda (3NaO, POj) ; and as this is the only salt that remains tribasic at a red heat, 

 he concludes that the alkalinity of the blood, as well as of the ash, is dependent on 

 it. Enderlin is the only chemist who excludes carbonates from the ash of the blood 

 and other animal fluids. The manner in which he accounts for the occurrence of 

 these salts in the analyses of other chemists is very plausible. On exposing 3NaO, 

 POj to the atmosphere, it becomes converted into 2NaO, HO, PO^ and NaO, COj. 

 (Liebig and Wohler's Annalen der Chemie imd Pharmacie; March 1844.)] 



