1873O New Facts concerning the Diamond. 441 



Profiting by the facilities offered by M. Daniels, a series 

 of experiments upon density were effected by M. von Baum- 

 hauer with all precautions required by this operation. 



The water used in the weighing was boiled and cooled in 

 vacuum, the temperature of the water and also that of the 

 air being noted. During the weighing of the diamond in 

 the air upon the pan of the balance, the platinum boat, 

 which was to receive the diamond for its subsequent weigh- 

 ing in water, was suspended to a human hair and already 

 plunged into the liquid, so that the determination of its 

 absolute weight and that of the loss in water should be 

 made under the same conditions, and consequently with the 

 same degree of accuracy. The pressure of the air having 

 varied only between 759 and 761 m.m. during these 

 experiments, it was considered unnecessary to correct for 

 variation of the barometer, such correction exercising no 

 influence upon the result, since the exactitude of this mode 

 of weighing in which there is friction of the hair against 

 the water attains at least the demi-milligramme. 



The subjoined table (see page 442) contains the result of 

 these experiments ; in the last column will be found the 

 calculated densities D, obtained by adding to the numbers 

 of the last column but one, the corrections arising from one 

 of the weighings having taken place in water at the tem- 

 perature U and not in water at 4 C, and from the other 

 weighing having been effected in the air at temperature t, 

 and not in a vacuum. 



This calculation was performed according to the known 

 formula : — 



D _P f/l _ P-P I ab 



P l t P 1 760(1 Xj3Q' 



where a = 0*00129337 grm., is the weight of a cubic centi- 

 metre of air at o° C.,and 760 m.m. of barometric pressure, and 

 @ = 0*00367 the coefficient of dilatation of the air; no cor- 

 rection having been made for the height of the barometer, 



— -=i was taken. 

 760 



On comparing the corrected densities in this table, it will 



be perceived that the purest diamonds possess the highest 



specific gravity. 



No. 1 3*51821 



» 2 3*52063 



» 3 3*51727 



» 4 3*5i63i 



» 5 3*51934 



