266 J. II Long — Circular Polarization of 



Attempts were made to prepare solutions containing salts of 

 thallium with the potassium antimony tartrate, but only very 

 dilute ones could be obtained. 



In the above table it will be observed that without exception 

 the specific rotation is decreased by addition of inactive salts, 

 this decrease being especially marked in the case of sodium 

 acetate. In the preparation of the solution with this salt it 

 was observed that heating must be avoided as this produced a 

 precipitate in a short time. It was also noticed that a solution 

 with 15 gm of sodium acetate gave a crystalline precipitate after 

 standing. The mixture, therefore, is not a very stable one, and 

 the greatly decreased rotation indicates that some change has 

 taken place, even before a precipitate appears. The precipi- 

 tation by acetates has been pointed out before, but attention 

 has never been especially called to it. 



It will also be noticed that the nitrates of sodium, and 

 ammonium produce a greater change than do the correspond- 

 ing chlorides, and finally that when several solutions with 

 the same inactive substance were tried the rate of increase 

 in the deviation from the normal specific rotation is a dimin- 

 ishing one with the concentration. 



Thallium Tartrate, T] 2 C 4 H 4 G B . |H 2 0. 



This salt was prepared from the sulphate which was first con- 

 verted into the hydrate by means of solution of barium hydrate. 

 The hydrate was neutralized with solution of tartaric acid, 

 the point of neutrality being shown by disappearance of re- 

 action with phenol -phthalein. The salt thus made was purified 

 by several crystallizations and was shown by analysis to have 

 the above composition, which agrees with the formula found 

 by Lamy and Des Cloizeaux (J. B. 1868, p. 254). 



5 grm. of the salt in 100 cc polarized in the 400 mm tube at 20° 

 gave 



a— 0°-950 

 from which [a] 4°'758 



Another solution was polarized at 19° and at 28°*4 giving 

 a 19 =0°-915 a 384 =l°-l.39 



[a] 19 =4°-582 [«] 3 8.4= 5 °^ 04 



From the mean of the observations we have 

 [a] 20 =4°-729 



This gives a marked increase by temperature. 



To test the effect of addition of inactive salts I prepared six 

 solutions containing, with 5 grm. of the tartrate, compounds of 

 sodium and potassium, and one with thallium sulphate, and 

 polarized them as before. The results are given in the table 

 below : 



