Constitution of the saline ingredieiits of Animal Fluids, 533 



sencc of alkaline carbonates in the ashy he has considered that 

 no combination of an organic acid with an alkali could have ex- 

 isted in the secretion yielding it. 



I confess, 1 always doubted the correctness of this opinion, 

 and hope now to adduce satisfactory evidence that a combina- 

 tion o^ an organic acid, "with an alkali may really exist in a solu- 

 tion of 2)hosphate of soda in considerable quantity^ andyet yield 

 no carbonate by ignition. 



If nine grains of dry tribasic phosphate of soda (HO, NaO, 

 PgOg) be mixed carefully with four of dry acetate of soda, 

 and the mixture exposed for a quarter of an hour to a full red 

 heat in a covered crucible, a snow-white spongy mass will 

 be obtained. This will be found to dissolve readily in water, 

 to exert a powerfully alkaline action on litmus-paper, and does 

 not evolve any bubbles of gas when dilute sulphuric acid is 

 added to its solution, or to a portion of the substance after 

 beinjr covered with water. The addition of nitrate of silver 

 to a solution of the salt produced a copious precipitate oiyel- 

 Iffw tribasic phosphate of silver. It is hence obvious that the 

 soda left by the ignition of the acetate of soda was sufficient to 

 replace the water in the phosphate, which thus became con- 

 verted into the sub-salt, the acid being, notwithstanding the 

 heat to which it had been submitted, in the same stale as that 

 existing in the common rhombic phosphate, in consequence of 

 the presence of three atoms of base. The reaction occurring 

 is simple enough. 



NaO, C4 Ha O3 -|- HO, 2NaO, Pj O5 = 3NaO, Pg O5 -|- CO2 HO -|- C3 H3 O, 

 The evolution and combustion of the acetone may be observed 

 when the mixed acetate and phosphate are ignited in a plati- 

 num spoon. 



It is assumed by Enderlin that the sub-tribasic phosphate 

 pre-exists in a secretion, when it is found in the ash obtained 

 from the incineration of its extract. Of this I venture to 

 assert we do not possess a single proof. The ordinary rhom- 

 bic phosphate is in all probability the compound which exists 

 in secretions; indeed in the urine very satisfactory evidence 

 can be obtained on this head. If urine be evaporated to an 

 extract and digested in alcohol, an insoluble residue contain- 

 ing chloride of sodium and rhombic tribasic phosphate will 

 be left: on allowing a drop of a watery solution of this salt to 

 evaporate on a plate of glass, penniform groups of crystals of 

 the rhombic phosphate mixed with common salt will be left. 



Without occupying further space by alluding to other less 

 important points of Enderlin's paper, I venture to hope I have 

 proved that the absence of a carbonate in an ash is by no 

 means a proof of the non-existence of salt of an organic acid 



