84 PROCEEDINGS OF THE AMERICAN ACADEMY 



We made four observations of the melting point of the hexagonal 

 iodide. For the first, we used a large amount of material, and, by 

 dipping the bulb of the thermometer in the melted mass, observed the 

 constant temperature while it was slowly solidifying. In the other 

 experiments, we melted a few crystals in a glass tube, heated by a bath 

 of sulphuric acid in the usual way. The result in the first determina- 

 tion was 167^°; in the last three, uniformly 167'^, which is doubtless 

 the true value. In the experiments with the tube, it was noticed that 

 the point o'f solidification was about five degrees below the melting 

 point. 



Bringing together now the several results, we have the following 

 comparison of the melting points of the three haloid compounds we 

 have studied — 



Melting Point. Differences. 



Rhombic Antimonious Chloride 72° 



Rhombic Antimonious Bromide 93'^ 



Hexagonal Antimonious Iodide 167° 



21' 

 74' 



From this it appears, that, instead of the equal differences we should 

 naturally expect, the difference between the last two values is between 

 three and four times as great as the difference between the first two. 

 According to all analogies, the melting point of the normal iodide of 

 antimony should be 114°; and the greatly higher value which we ob- 

 tained is still another indication that the hexagonal iodide on which 

 we experimented has an essentially different structure from that of tne 

 chloride or bromide of the same element with which it is here com- 

 pared. 



As yet, we have not been able to determine the boiling point of 

 iodide of antimony with any accuracy. It is above, but apparently 



