104 § 73. BASES AND ACIDS WITH REAGENTS. 



MALIC ACID. H2C4H4O5. 134. 



73. Malate of lead is difficultly soluble in water 

 Reactions; — When malic acid is heated, it froths, pun- 

 gent acid vapors being set free, and crystals of maleic and 

 fumaric acids are condensed in the colder parts of the 

 tube. 



Malates give no precipitate with potassic salts, nor 

 with calcic hydrate or sulphate, even on boiling. 



With calcic chloride no precipitate is formed unless the 

 solution is concentrated and the mixture is boiled ; if this 

 precipitate, CsiCJIfi^,21Ifi, is dissolved in a very little 

 hydrochloric acid, ammonia added, and the mixture boiled, 

 the calcic malate is re-precipitated ; but if it is dissolved 

 in considerable acid, no precipitate is formed on adding 

 ammonia and boiling ; alcohol will precipitate the salt 

 from this solution. 



Quantitative estimation. — An approximate determina- 

 tion of malic acid may be made by adding calcic hydrate 

 in excess to its highly concentrated solution, free from 

 citric, tartaric, or sulphuric acid, and then adding consid- 

 erable alcohol, collecting the precipitate on a dried and 

 weighed filter, washing with alcohol, drying at 100° C, 

 and weighing. 



The residue contains 67.44"|„ of malic anhydride, 



LACTIC ACID. nCaHgOs. 90. 



74. All lactates are soluble in water ; only zincic lactate 

 is somewhat difficultly soluble in cold water. 



Reactions. — Lactates are blackened when heated. 



If a liquid containing free lactic acid is boiled with zin- 

 cic oxide or carbonate, the filtered solution will deposit a 

 crystalline crust on its surface, or acicular crystals, on 

 cooling. 



