108 KELLER AND MA AS — DIMETHYL RACEMIC ACID. [April 7, 



ethyl racemates were observed, which rendered a more elaborate 

 study of these salts desirable. This was the object in the experi- 

 ments recorded on the following pages. 



The neutral salts of sodium, potassium and ammonium, which are 

 very soluble in water, were made by neutralizing weighed portions 

 of the acid with calculated quantities of the alkaline carbonates or 

 ammonia, and evaporating to crystallization. 



Sodium dimethyl racemate, CgHgOgNaa + 4H0O, forms minute, 

 efflorescent needles. A freshly prepared specimen yielded 23.85% 

 of water, while two others which had been exposed to the air for 

 some time, gave 17.65% and 16.14% respectively. Theory re- 

 quires 24.48%. The amount of sodium in the anhydrous salt was — 



Required. Found. 



Na 20.72% 20.75% 



Both the neutral and the highly characteristic acid potassium 

 salt have been previously described. A new determination of the 

 potassium contents of the latter gave 17. 8^%, instead of 18.05% 

 required. 



The " Rochelle Salt " of dimethyl racemic acid appears to have 

 the composition CgHgOgKNa -f- 2H2O. Its preparation and analy- 

 sis were attended with many difficulties. On neutralizing the acid 

 potassium salt with sodium carbonate and carefully evaporating the 

 solution, a homogeneous crop of crystals was obtained, but on further 

 evaporation the liquid deposited a mixture of efflorescent prisms 

 and wart-like aggregations of clear anhydrous crystals. An analysis 

 of the first product yielded — 



Required. Found. 



H2O 13-14% 12.00% 



K (calculated for anhydrous compound) 16,25 " 16. 12 " 



Na " " " 9-58" 9-49" 



Unlike the salts of the alkali metals, those of the alkaline earth 

 and heavy metals are insoluble or nearly insoluble in water, though 

 in a few instances they are difficult to precipitate. Many of the 

 insoluble salts contain water of crystallization, which they tena- 

 ciously retain at high temperatures. In some cases the composi- 

 tion corresponds to that of the racemate, in others there are notable 

 differences both in composition and properties. 



The calcium salt which, owing to its great insolubility, was 

 recommended by Fittig and Keller as the most delicate means of 



