282 J. H. Long — Polarization of Tartrate Solutions. 



These results are illustrated by the curve E. The solutions, 

 after boiling, were strongly acid. Several tests were made 

 with borax solutions in the same manner. They gave tests for 

 free boric acid while the precipitate formed had the composi- 

 tion observed in the other cases. 



From a consideration of the behavior of the several mixtures, 

 I think it is plain that the explanation of the decrease in the 

 rotation must be the same for all cases. This explanation is 

 one which at first sight would scarcely be expected because of 

 the practical silence of the literature on the subject of carbon- 

 ates, acetates and phosphates of antimony. The last two have 

 been described as stable in some of the older works. If we 

 may assume that in these combinations the metal is held as 

 SbO' the polarization phenomena can be readily accounted for. 

 By mixing solutions of alkali phosphates, acetates, carbonates 

 and borates with the tartrate in the cold there is probably first 

 formed a temporarily stable antimony salt with corresponding 

 amount of alkali tartrate. The observed rotation is due to this 

 plus that of the unchanged potassium antimony tartrate. After 

 decomposition by heat a small amount of free tartaric acid or 

 bitartrate, with low rotation, must exist in the cases where 

 acetic and phosphoric acids had been liberated in the reaction. 

 In the solutions with large excess of carbonate the total anti- 

 mony found probably exists in combination with sodium, the 

 decomposing action of the carbonate being much greater than 

 that of the phosphate, acetate or borate. 



Experiments with potassium ammonium tartrate. 



I have already shown that the rotation of solutions of potas- 

 sium sodium tartrate is in general increased by addition of 

 salts of potassium or ammonium and decreased by those of 

 sodium and lithium. I have since carried out a similar 

 investigation, using potassium ammonium tartrate as the 

 active substance. This salt was freshly prepared from pure 

 KHC 4 H 4 6 and JSTH 4 OH and crystallized. In the following 

 table I give a few of the results obtained which illustrate all. 



20 grins, of KNH 4 C 4 H 4 6 in lOOc.c. gave at 2Q° a = 24°-680, 

 or [«] — 30° "850, which is somewhat lower than the value given 

 by Landolt. In presence of inactive salts the rotation is 

 altered as here shown. 



In 100 c.c. with 







Deviation 



20 grms. tartrate. 



«D 



Md 



in [a]. 



5 grins. NH 4 C1 



24°-525 



30°-656 



— 0-194 



10 NH 4 C1 



24°-480 



30°-600 ■ 



— 0-250 



5 KCl 



24°-no 



30°'888 



+ 0-038 



10 KCl 



25°-136 



31°-420 



+ 0-570 



5 NaCl 



23 o> 790 



29°'963 



— 0-887 



10 NaCl 



22°-806 



28°-508 



— 2-342 



