274 J. H. Long — Circular Polarization of 



warming. In these cases clear solutions could be prepared by 

 mixing in the cold. 



In seeking for an explanation of this curious behavior I 

 found that the several samples of bromides employed in these 

 last tests were not absolutely pure, but contained traces of car- 

 bonates, which would account for the precipitation of the 

 antimony by heat. This suggested the use of a pure carbonate 

 with the potassium antimony tartrate, and after a time I suc- 

 ceeded in making, at a low temperature, a clear solution con- 

 taining in 100 cc. 5 gm. of the tartrate and 1 gm. of dried 

 sodium carbonate (Na 2 C0 3 -fl|-H 2 0). This, on polarization in 

 the 400 mm. tube, gave a most remarkable result : 



8°-5 





« = 11°-140 £=1 



or 



[a] = 55°-795 (cor.), 



instead of 



141°-2V3. 



Here we have a loss of over 60 per cent and without appar- 

 ent decomposition. However a very slight elevation of temper- 

 ature was sufficient to produce a precipitation of the antimony, 

 and it was also found that on standing in the cold a similar 

 precipitation took place. 



It was found that with care solutions containing the potas- 

 sium antimony tartrate with phosphates and borates could be 

 prepared at low temperatures. With a solution of 5 gm. of 

 the tartrate and 1 gm. of ordinary sodium phosphate I observed 



a— 25°'244 «=18°-5 



[a] = 126°-334 (cor). 



Slight warming decomposed this solution. 



Now, what is the condition of the antimony just before pre- 

 cipitation here ? In view of all the facts I believe it must be 

 looked upon as an unstable oxy carbonate or phosphate, held in 

 solution by the tartrate, and ready to precipitate by change of 

 temperature or on standing. It has probably already left the 

 tartrate group and its place has been taken by something else 

 giving a lower rotation. On this hypothesis the phenomena 

 observed with the thallium antimony tartrate can also be 

 explained, but until such an investigation as I suggested above, 

 in presenting the experimental data, is carried out, a fuller con- 

 firmation cannot be given. In such an investigation the be- 

 havior of many solutions, in what I have called a condition of 

 unstable equilibrium, should be studied, and the polarizations 

 should be made not only at low temperatures but at the highest 

 temperature possible before precipitation actually takes place. 

 Freshly prepared solutions and those which have stood should 

 also be tried. Such an investigation I plan for the near 

 future. 



