138 LACTIC ACID. 



.11. Heat a kryptophanate in the solid state on 

 platinum foil : acid vapours are perceived but no 

 iirinary smell, and a residue of difficultly combustible 

 charcoal remains. 



12. Add baryum or calcium chloride : no precipitate. 

 Add ferric chloride : a brown precipitate will fall, 

 soluble in excess or in ammonia, deposited again on 

 boiling. 



Lactic acid, C 3 H 6 3 (from milk). 1. Take 300 

 grammes of sugar, 3 grammes of tartaric acid, 400 

 grammes of sour milk, 25 grammes of old cheese, and 

 150 grammes of precipitated chalk, and 1250 cc. of 

 water ; allow to stand in a moderately warm place, about 

 36 C., from ten to twelve days. Boil the semisolid 

 mass of calcium lactate thus produced with a litre of 

 water and 3 grammes of unslaked lime ; filter while hot 

 and gently evaporate the filtrate. Calcium tartrate is 

 gradually deposited in granules. Collect the crystals 

 and press between filter paper. Dissolve the crystals 

 in twice their weight of water, add -% part of sul- 

 phuric acid and filter while hot ; add to the filtrate - x % 

 of zinc carbonate, boil for a quarter of an hour, separate 

 the crystalline zinc salt, dissolve in seven to eight times 

 their weight of boiling water, pass in sulphuretted 

 hydrogen, filter and evaporate to a syrupy condition. 



2. Boil some lactic acid with nitric acid; the lactic 

 will be converted into oxalic acid : neutralise the 

 liquid with ammonia, add acetic acid and a little 

 calcium chloride solution ; calcium oxalate will be 

 precipitated. 



