1904.] 



On the Compressibility of Solids. 



307 



In the summary, Table VII, the compressibilities of English flint 

 glass and of the glass of which ordinary German tubing is made as well 

 as that of mercury have been included for purposes of comparison. 

 The compressibility of mercury rests upon a large number of observa- 

 tions made in the " Challenger,"* by which its apparent cubic com- 

 pressibility was found to be 1*5 per million per atmosphere. The 

 piezometers which were used for this purpose were made by myself on 

 board. The divided stems were of lead glass, because I had no other, 

 and the bulbs or reservoirs, which had a capacity of about 20 c.c, were 

 made of German glass, for the same reason. I have, therefore, applied to 

 the values then found for the apparent compressibility of mercury, the 

 value of the absolute compressibility of German glass found in January 

 of this year, and the result is that the absolute cubic compressibility of 

 mercury at temperatures between 1° and 3° C. is 3*99. 



With regard to the metals quoted in the tables, the figures speak for 

 themselves. The number of different metals is very small and, until 

 the investigation has been extended so as to include at least the greater 

 number of the metals which can be easily procured in the form of rod 

 or wire, it is not likely that any very general features or laws will be 

 apparent. It will, however, be observed that in the case of the five 

 metals used as wire, their compressibility increases as their density and 

 atomic weight diminish, yet there is no reason to suppose that the 

 compressibility is a continuous function of the atomic weight, like the 

 specific heat. Mercury, although in the fused state, shows this clearly. 

 But besides this, it happens that two pairs out of the five metals, 

 namely, platinum-gold and aluminium-magnesium, are contiguous in 

 the atomic weight series, yet the compressibility of magnesium is, 

 roughly, double that of aluminium, and the compressibility of gold is 

 half as much again as that of platinum. If, however, we compare gold 

 and copper, which occupy parallel positions in MendeleiefFs scheme, 

 we see that they are very much alike, and the same holds with regard 

 to magnesium and mercury which occupy a homologous position. If 

 these facts indicate anything more general, we should expect the 

 metals of the palladium and the iron groups to have a low compressi- 

 bilitylike platinum, zinc and cadmium to have a very high compressibility 

 like magnesium, and thallium an intermediate but still considerable 

 compressibility like aluminium. 



It will be observed that the two kinds of glass mentioned in 

 Table VII are more compressible the greater their density. This may, 

 however, be due to a specific feature of the oxide of lead which enters 

 largely into the composition of the flint glass. 



It is obvious that there is here a great field for interesting research, 

 and fortunately the method is capable of great refinement ; only, the 

 successful application of it requires considerable manipulative skill, 

 * ' Chem. Soc. Jour.' (1878), vol. 33, p. 453. 



