1877.] 



Density of Solid Mercury. 



75 



Applying the correction for capacity of vessel at the respective tempe- 

 ratures, the three results were : — 



cub. centims. grms. 

 59-6625 of alcohol at -37° C. =50-7010 

 59-6600 „ „ -40° =50-8316* 

 59-6576 „ „ -42°-5 =50-9092 



or, reducing to one common weight, 



cub. centims. grms. 



117-6752 of alcohol at -37° =100 



117-3679 „ „ -40° =100 



117-1843 „ „ -42°-5 =100 



(10) Taking the difference between (a) the first and second, (b) the 

 second and third, and (c) the first and third of these numbers, and dividing 

 each difference by the number of degrees in the interval of temperature, 

 we get as the change of volume of 100 grammes of alcohol for 1° C. : — 



cub. centim. 



From (a) -1024 



(&).... -0734 



(c) -0893 



and the mean of these (-0884) may be taken to represent the coefficient 

 for 1° C. within a range of a few degrees either side of the freezing-point 

 of mercury. Using this coefficient to reduce the three weighings to their 

 corresponding values for the same temperature, say —39° C, we have 



grms. cub. centims. 



100 of the alcohol in question at -39° =117*4984 

 ,, „ „ „ ,, =117*4563 



,, „ „ ,, „ =117*4937 



the mean of which is 117*4828 cub. centims. 



(11) The specific-gravity flask having been emptied and dried, 558*9353 

 grammes of mercury was introduced, the metal having just previously been 

 purified by careful treatment with dilute nitric acid, washing with water, 

 and quiet distillation from a g]ass retort. Pilling up with the same al- 

 cohol as that used in the above experiments, and which had been kept 

 in a well-stoppered bottle, the flask was gradually cooled, and finally, in 

 the last freezing-mixture, the mercury frozen, and the alcohol brought 

 exactly to the mark, taking care that it became and remained quite sta- 

 tionary, while during the freezing of the mercury the change of volume 

 was very rapid and easily observable. The temperature having been 

 noted when the final adjustment was made, the little flask was set aside, 

 stoppered, until it could be washed off and dried, and was then allowed 



* This weighing was not quite so satisfactory as the remainder ; the temperature a 

 little doubtful. 



