1904.] KELLER AND MAAS — DIMETHYL RACEMIC ACID. 109 



recognizing the presence of dimethyl racemic acid, is at once pre- 

 cipitated when calcium acetate or gypsum solution is added to that 

 of one of the soluble salts. It may be obtained in a crystalline 

 form by dissolving it in hydrochloric acid and reprecipitating with 

 sodium acetate. Its composition varies considerably according to 

 the conditions under which it is formed. The water of crystalliza- 

 tion is not completely expelled below 215°, a temperature just 

 below incipient decomposition. The following are a few of the 

 analyses made of this salt : 



Required. Found. 



I mol. H2O i;^ mol. HjO L II. III. 



H,0 7.65/^ 11.11% 7.38% .... 11.39% 



Ca 17-05" 16.46" 17.20" 16.12 16.33" 



The bariu7n salt, CgHgOg Ba -j- 2 HoO, shows a remarkable re- 

 semblance to the corresponding racemate, from which it differs, 

 however, in that it contains one-half molecule less of water of 

 crystallization. This point has been established by comparative 

 analyses of both compounds. The results were-^ 



Racemate. Dimethyl racemate. 



Required, Found. Required. Found. 



Uf> ....13.64% 13-52% 10.32% 10.12% 10.42% 



Ba 41.40" 41.10" 39-25" 39-14'* 39.16" 



Magnesium salt, CcHgOgMg -f- HjO. A white bulky precipitate. 

 The air-dried substance gave — 



Required. Found. 



H.O ,... 8.25% 7.06% 



Mg ii.oi " 10.95 " 



Manganese salt, CeHgOgMn -f ^^HaO. Forms a crystalline 

 precipitate having a faint pink tint. The formula is derived from 

 these results : 



Calculated. Found. 



H2O 3.75 % 3.72% 



Mn 22.91 " 22.97 " 



The zinc salt, CcHgOgZn -f H2O, is obtained as a granular, 

 white precipitate when zinc acetate is added to an alkaline salt of 

 dimethyl racemic acid. It is almost insoluble in water and in 

 dilute acetic acid. Determinations of the water of crystallization 



