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



angle of rotation varies regularly with the amount of added 

 carbonate, the reaction not being at all obscured by precipita- 

 tion. A molecular re- arrangement of some sort, undoubted]}' 

 an interchange of bases, must take place here. In the solu- 

 tions prepared at the boiling temperature the decrease in the 

 rotation is rapid until we pass the one containing - 8 grm. of 

 the carbonate, which is theoretically sufficient for complete 

 precipitation. In the solutions with larger amounts of the 

 carbonate the change in the rotation is slow, as shown in the 

 curve C. In the fourth column of the table above I give the 

 amounts of potassium antimony tartrate left in solution, as 

 determined by precipitation of the antimony as sulphide, and 

























































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calculated on the assumption that it is held as tartrate and not 

 as antimonite or other compound. In column five are given 

 the rotations calculated for these amounts of the antimony 

 potassium tartrate plus that of the sodium potassium tartrate 

 formed corresponding to the decrease in the other. In column 

 six are given results calculated on the assumption that the 

 added sodium carbonate precipitates antimony in the propor- 

 tion given in the equation above. On this assumption for 

 solutions containing more than - 7982 grm. of the carbonate the 

 rotation should be that of the Rochelle salt equivalent to 5 

 grms. of the antimony compound taken. In the values given I 

 have not taken into consideration the slight decrease in the 



