certain Tartrate Solutions. 271 



5gm. of ammonium nitrate [a] = 11 0, 355, with 5 gm. of 

 sodium sulphate [a] = 11°'418, with 5 gm. of potassium nitrate 

 [a] = 11°-155, while with the 10 gm. of tartrate and 5gm. of 

 thallium sulphate I found [a] = 6° '793. 



Thallium Ammonium Tartrate, T1NH 4 C 4 H 4 6 . 



The crystals not appearing to be uniform in composition, I 

 prepared solutions as desired by mixing calculated amounts of 

 thallium bitartrate and ammonium hydrate. The results ob- 

 tained by testing four solutions are given here. 



gm. in 100 cc. D 2 4 ° P a [a] 



5 gm. T1NH 4 C 4 H 4 6 1-0354 4*821 2*003 10-032 



10 " " " 1-0726 9-306 3"520 8-815 



15 " " " 1-1092 13 499 4'740 7"914 



a0 " " " 1-1459 17-423 6-040 7"563 



The rate of decrease in the specific rotation with increase in 

 concentration is very nearly the same as with the preceding com- 

 pounds and is illustrated in the curve A. For t = 31° the 

 10 gm. solution gives a = 4°'142, which is a more rapid rate of 

 increase than with the potassium thallium salt. 



The results obtained by adding inactive salts are quite 

 analogous to those found in other cases ; thallium sulphate 

 decreases the rotation, while the sulphates of potassium, so- 

 dium and ammonium increase it. 



Potassium Boro- Tartrate, KBOC 4 H 4 6 . 



This salt was prepared in the usual manner by heating a 

 mixture of 3 parts of potassium bitartrate, \\ parts of boric 

 acid and 10 parts of water to complete solution. The liquid 

 was then brought to the boiling point and evaporated to dry- 

 ness. The residue was powdered and washed thoroughly with 

 alcohol to remove excess of boric acid. It was afterwards 

 dried in the air and then over sulphuric acid. Four solutions 

 of this preparation, gave at 20° : 



C= 5, [a] = 53°-070, C = 15, [a] = 61°-V03 



C = 10, [a] = 59°-055, C = 20, [a] = 62°-621 



For the 10 gm. solution I found, after determination of the 

 density, 



[a] 29 = 57°-286 



showing a decrease in the specific rotation by increase of tem- 

 perature. 



The increase with greater concentration is very marked, and 

 the reverse of what was shown to be the case with the 

 thallium solutions. Further experiments were tried with some 

 of the boro-tartrate dried at 100°, it being evident that a small 



