410 Mr. S. U. Pickering on the Expansion 



sion of a solid must imply sudden changes in its constitution, 

 just as they do in the case of a liquid ; and in the case of a 

 solid, where the molecules are practically fixed, such changes 

 present far greater difficulties than in the case of liquids, 

 where the mobility of the particles is great, and where we 

 have a state particularly favourable for dissociation. 



An examination of the densities of some other liquids has 

 added confirmation to my conclusions respecting water. The 

 changes which they exhibit are placed at various temperatures, 

 showing that they cannot be attributed to constant errors in 

 the instruments used, and some of them are moreover of a 

 much more pronounced character than those in the case of 

 water. 



Pierre's memoir above cited gives the results obtained with 

 eleven other liquids ; these I have differentiated directly, and 

 the differentials are plotted out in Plate VIII. They are 

 arranged roughly according to the magnitude of the rate of 

 change : the scale adopted for dv/dt, it must be specially 

 noted, is only one-fifth of that used in Plate VII. 



With ethyl chloride the results are not very regular : they 

 appear to form a continuous straight line throughout. 



With methyl bromide they form a slight curve continuous 

 throughout, but there are not sufficient points to admit of any 

 definite conclusions being drawn from them. 



In the case of ether we get two straight lines meeting at 

 about 14°, and showing the existence of a change at that 

 temperature, which is further emphasized by the very non- 

 conformable point existing there (see Trans. Chern. Soc. 1890, 

 p. 67). There seems to be another change at —10°, but the 

 data are insufficient to prove it. 



With ethyl formate the results are represented by a straight 

 line from 60° to —21°, where there seems to be a change ; 

 but it is uncertain in its character. 



Ethyl bromide gives two straight lines showing a change 

 at about 39°. 



With methyl acetate we get a continuous and very slight 

 curve ;' but it might well be a straight line from 65° to about 

 — 1 0°, followed by a different line down to — 34°. 



Methyl iodide gives two straight lines showing a change at 

 10°. The points are not in very good agreement with the 

 upper of these two lines, but if we take the means between 

 consecutive points the agreement is perfect. 



Methyl alcohol gives three straight lines with changes at 

 44° and 16°. 



