300 Mr. T. E. Thorpe on the [Feb. 17, 



The rate of expansion of bromine has already been determined by 

 Pierre, who has given the following expression to represent the results 

 of his observations * : — 



V=l + 0-001 038 186 255* + 0-000 001 711 380 853* 2 



+ 0-000 000 005 447 118 1\ 



This formula gives numbers agreeing fairly well with those afforded 

 by the expression deduced from my determinations, as the following 

 comparison shows (the temperatures are given in degrees of the mer- 

 curial thermometer) : — 



15° 30° 45° 60° 



Pierre 1-01608 1-03273 1-05068 1-06963 



Thorpe 1-01624 1-03326 1-05108 1-06960 



Pierre was undoubtedly one of the first to obtain bromine in a state 

 approaching to purity ; but it seems probable, in spite of the care which 

 was evidently taken in its preparation, that the sample employed by him 

 in his determination of its rate of expansion was not perfectly free from 

 water. This is indicated by the order of the divergence between the 

 results of our various observations ; and the supposition would seem to be 

 confirmed by the high solidifying-point, viz. — 7 C '5 to —8°, which he 

 observed. Baumhauer has shown that the true freezing-point of bromine 

 is at — 24°-5t. Pierre sought to dry his bromine by digestion with 

 calcium chloride. According to Stas, calcium bromide (which, as a 

 desiccating agent is not inferior to the chloride) is incapable of removing 

 the last traces of water from bromine J. 



The specific volume of bromine, calculated from Pierre's numbers, is 



159-90 



2-96881 



53-859. 



II. Iodine Monochloride. 



Prepared by heating an intimate mixture of iodine and potassium 

 chlorate, and distilling the product from powdered potassium chlorate, 

 I 2 + 3KC10 3 =KC10 4 +KI0 3 +KCl + 2 +ICl. 



The product was repeatedly distilled in order to break up the last traces 

 of the yellow iodine trichloride which is always formed in slight quantity 

 in the preparation. The liquid ultimately boiled constantly between 

 99°-7 and 100°-7 ; n=40°, t' = 75°. Corrected and reduced barometer 

 744-3 millims. Corrected and reduced boiling-point 101 o, 3. 



In order to establish its purity the iodine monochloride was analyzed 

 by breaking bulbs containing weighed portions of the liquid under dilute 



* Ann. de Chim. et de Phys. [3] 20. t Deutsch. Ch. Ges. Ber. 1871, p. 927. 



\ Stas, Nouvelles Recherches sur les Lois des Prop. Chem. &c. Aronstein's German 

 translation, p. 179. 



