certain Tartrate Solutions. 



273 



point to a law which may be stated in this way : the rotation 

 of a double tartrate may be made to approach that of a neutral 

 tartrate of either of the metals present by addition of a salt of 

 that metal. In the case of Rochelle salts I tried to explain 









































































































































































3 























































































t-C 































































































































-E 































































































































1 













. 











/ 













A 



r 









Pi 



> 



this by assuming that a substitution took place in the solution ; 

 that is, for instance, that by adding potassium chloride to a 

 solution of sodium potassium tartrate the latter was converted 

 more or less perfectly into neutral potassium tartrate. The 

 same explanation would evidently hold for the other solutions. 



But when we come to a consideration of the compounds con- 

 taining antimony and boron we find several difficulties. Tak- 

 ing up the antimony potassium tartrate first, we notice that the 

 slight decrease observed in several cases can be explained by 

 assuming the displacement of the potassium, but this will not 

 account for the decrease in the rotation in the cases where 

 potassium salts were the inactive bodies added, nor for the very 

 great decrease in the solutions containing acetates. 



I am inclined to think that we must assume here a replace- 

 ment of the antimony radical ; but how ? In what form can 

 we suppose it to exist if withdrawn from the tartrate group? 

 Most of the antimony compounds which could be formed in 

 this way are usually considered insoluble, but unfortunately 

 we have no very full data on the subject. . A few experiments 

 of my own may give a little light here. I mentioned above 

 that the solution containing acetates had to be prepared in the 

 cold to avoid precipitation of the antimony. I observed also 

 that several solutions containing bromides could be maae clear 

 by boiling the tartrate and bromide together, while with 

 others precipitation of the antimony took place even on slight 



Am. Joub. Sci— Third Series, Vol. XXXVIII, No. 226, 

 18 



-October, 1889. 



