1877.] 



Density of Solid Mercury. 



73 



smaller size, the upper and open end of the shortened tube of which was 

 fitted with a small carefully ground glass stopper. The neck between 

 the larger and smaller cylinders was drawn down to a small bore (about 

 2 millims.), and at this narrowed part a fine line marked round it with a 

 diamond. The shape of the vessel is shown in the annexed sketch, on a 

 linear scale of one half the real size. The principal cylinder held about 

 58 cubic centimetres, and the small reservoir above 25 cub. centims. 

 The whole vessel weighed about 46 grammes. 



It enabled the experiments to be carried out with more than half a 

 kilogramme of frozen mercury. 



(2) This vessel having been accurately weighed when empty and dry, 

 its capacity up to the mark was ascertained by filling it to this point 

 with pure water at exactly 4° C, keeping it immersed for some time in a 

 large mass of water at this temperature before making the final adjust- 

 ment to the mark, wiping the outside dry, allowing the whole to acquire 

 the temperature of the balance-case, and carefully weighing. The result 

 of this direct calibration, deducting the weight of the vessel, was 59*7323 

 grammes or cubic centimetres at 4°. 



(3) It was checked by emptying and drying the vessel, filling it to the 

 mark with pure mercury at 0° C, the temperature being secured by keep- 

 ing the whole surrounded by melting ice long enough to obtain perfect 

 steadiness of position of the mercury, and weighing after the tempera- 

 ture of the balance-case had been regained. The mercury weighed 

 811-9997 grammes. 



(4) The vessel was now surrounded by steam, and the mercury again 

 brought to the mark, the temperature actually attained being 99°*5 C. (cor- 

 rected for pressure). Allowed to cool down to the temperature of the 

 balance-case, and again weighed, the mercury was found =799*7032 

 grammes. From the last two weighings the coefficient of cubical expan- 

 sion for 1° 0. of the glass used was, by the usual formula (taking absolute 

 expansion of mercury from 0° to 100 ='018153, as determined by Beg- 

 nault), found =-000027346. 



(5) If now the density of mercury at 0° as referred to water at 4° be 

 taken at 13*596 (Eegnault), the weighing obtained in (3) gives the capa- 

 city of the vessel up to the mark at 0° =59*7234 cub. centhns., or, ap- 

 plying the above coefficient of expansion of glass, 59*7300 cub. centims. at 



59*7300 | 59*7323 



4°. The mean of this value and that obtained in (2), = ^ 



= 59*7311 cub. centims., was taken to represent the true capacity of the 

 vessel at 4°. 



