72 



Prof. J. W. Mallet on the 



[Mar. 15, 



Sp. gr. of solid mercury. 



Schulze 14-391 



Biddle 14-485* at -60° C. 



Kupffer and Cavallo 14 (approx.) 



Joule 15-19 



The last of these numbers, on reference to the original paper t, turns 

 out to represent no actual experiment with mercury itself, but is .the 

 density calculated for this metal from the examination of a number of 

 amalgams. Kupffler and Cavallo do not profess to give the exact density, 

 but merely state it as about 14, the number apparently resting on no 

 special experiment, though I have not been able to verify this by refer- 

 ence to their paper +. The only other apparently independent statement 

 I have met with occurs in the ' Annuaire du Bureau des Longitudes 9 for 

 1876 (p. 385), where the density 14-39 is given on the authority of Eivot ; 

 but I have not been able to find any reference to a paper by him bearing 

 on this or any analogous point, and it seems probable that we have here 

 only a reproduction of Schulze's result. In different handbooks of chem- 

 istry and physics numbers between 14 and 15 are given as approxima- 

 tions, but with no other authority than some of the above. Some of the 

 best and most recent works simply state that mercury undergoes consi- 

 derable contraction in freezing. Hence our knowledge on this subject 

 appears hitherto to have rested on the experiments of Schulze and Biddle, 

 both of which date back to the early years of the present century. 

 Schulze's paper was published in ' Gehlen's Journal/ vol. iv. p. 434, and 

 therefore about 1807 or 1808, and Biddle's§ belongs to the year 1805. 

 I have had access to neither ; but the character of the instrumental means 

 (balances, thermometers, &c.) generally available at the time the experi- 

 ments were made, and the then imperfect knowledge of the constants 

 needed for corrections to be applied, make it unlikely that very exact 

 results could have been obtained. Biddle alone seems to have noted the 

 temperature of the frozen mercury, and Branded expresses doubt that 

 this was determined with much accuracy. The temperature — 60° C, if 

 correctly quoted, is in itself somewhat improbable. 



The method adopted in the experiments lately made in this laboratory 

 was the following : — 



(1) A specific-gravity flask was prepared from a large cylindrical pi- 

 pette by closing in and smoothly rounding in the flame of the lamp one 

 end of the cylinder, while the tube remaining attached to the other end 

 was cut short and united by fusion to a second pipette of like shape but 



* 14465 as quoted by Brande in his ' Manual of Chemistry.' 

 t Chem. Soc. Journ. [2] i. p. 387. 



I Quoted at second hand from Playfair and Joule, " On Atomic Volume and Specific 

 Gravity," Chem. Soc. Mem. 2 (1845), p. 401, and 3 (1848), p. 57. 



§ Nicholson's Journal, ?ol. x. p. 253, and Tilloch's Philos. Mag. vol. xxx. p. 134. 

 || Manual of Chemistry, vol. i. p. 070. 



