URINE. 121 



ash, although there has been a large proportion of lactic acid 

 in the urine ; for if the urine contained only free lactic acid, or 

 lactate of ammonia, or even the lactates of soda and potash, at 

 the same time with phosphate of ammonia or chloride of ammo- 

 nium, the ash might be devoid of carbonic acid, in consequence 

 of the liberated phosphoric or hydrochloric acid uniting with 

 the base. 1 



In this case the lactic acid would have to be determined 

 analytically. The alcohol- extract of the urine contains both 

 free lactic acid and alkaline lactates ; after dissolving it in ab- 

 solute alcohol, precipitating the bases by sulphuric acid, filtering, 

 evaporating the alcohol, dissolving the residue in water, and 

 digesting the acid solution with oxide of zinc, we obtain a lac- 

 tate of zinc, which may be decomposed by free baryta. This is 

 certainly a very tedious proceeding for the mere qualitative de- 

 termination of lactic acid, and need never be adopted : since, 

 as far as I am aware, the ash (more especially the ash of the 

 spirit-extract,) always contains carbonates, and as the presence 

 of lactic acid in healthy urine has been sufficiently proved by 

 Berzelius. 



[It is well known that Liebig denies the existence of lactic 

 acid and the lactates in the urine ; and as the subject has re- 

 cently attracted much attention, I have thought it advisable to 

 state the grounds upon which that chemist has arrived at his 

 conclusions. " Lactic acid," he observes, " is a non-nitrogenous 

 substance. Nothing has hitherto been observed tending to show 

 that it may be produced from the elements of a nitrogenous 

 substance, by the decomposition of such a substance and the 

 transposition of its elements. In every instance where the for- 

 mation of lactic acid has been observed, the result of careful 

 examination has proved the presence of a non-nitrogenous sub- 

 stance of an identical, or, at least, similar composition with 

 that acid. 



1 [It has been recently shown by Dr. Golding Bird that an alkaline acetate (and 

 the observation applies equally to a lactate) may exist in a solution of phosphate of 

 soda in considerable quantity, and yet yield no carbonate by ignition. The reaction 

 is explained by the equation : 



NaO, C 4 H 3 3 +HO, 2 NaO, P0 5 =3 NaO, P0 5 +C0 2 , HO-f C 3 H 3 O. 

 (Lond. and Edin. Phil. Mag., June 1845.)] 



