ACETIC ACID. 85 



At a red heat lactates with fixed bases are converted into 

 carbonates : 100 parts of the carbonates of potash and soda cor- 

 respond to 180-9 and 201-1 parts of the respective lactates of 

 those bases. 



There is no ready test by which we can detect the presence 

 of lactic acid : it is chiefly distinguished by its negative pro- 

 perties. Rules for the quantitative determination of this acid 

 and its salts will be found in the chapters on the difterent fluids 

 in which it occurs ; they are founded with various slight modi- 

 fications on the method that we have given for the exhibition 

 of the acid. 



2. Oxalic acid is not one of the normal constituents of the 

 animal organism; it is however, when combined with lime, a very 

 common ingredient of morbid urine, and of urinary calculi. 



Oxalate of lime, when obtained by the addition of a soluble 

 oxalate to a salt of lime, occurs as a white amorphous powder, 

 insoluble in water, alcohol, oxalic and acetic acids, but soluble in 

 hydrochloric and nitric acids without efiervescence. It leaves, 

 when heated to incipient redness, a white residue of carbonate 

 of lime, from which the amount of oxalate may be easily calcu- 

 lated, for 100 parts of carbonate of lime correspond with 128-9 

 of oxalate of lime. After a prolonged exposure to a higher tem- 

 peratiu-e, the carbonic acid is expelled, and caustic lime remains. 



The occurrence of oxalate of lime in a crystalline state in 

 urinary sediments has been shown, by Dr. G. Bird, to be 

 much more frequent than was formerly supposed; in fact, 

 although the beautiful octohedral forms in Avhich it occurs 

 had been noticed some years ago by Vigla, Donne, and other 

 French observers, it was not until the appearance of Dr. G. 

 Bird's papers in the ' London jNIedical Gazette' for 18J;2, that 

 their chemical nature was fully established. 



3. Acetic acid has been found by Tiedemann and GmeHn in 

 the gastric juice, by Thenard in the sweat, by Simon in the 

 fluid of pemphigus and in saliva, and is asserted by some 

 chemists to be a constituent of m-ine. For its chemical cha- 

 racters we must refer to any of our systematic treatises on 

 Chemistry : it is sufficient to notice the means by which it may 

 be recognized, and its amount determined. Acetic acid may 



