244 



DE. A. MATTHIESSEN ON THE EXPANSION 



For sake of comparison I have given in Table XI. the values obtained by different 

 experimenters for the expansion of water, taking in all cases its volume at 4°=l-000000. 



Table XI. 



Kopp, Despeetz, and Pierre used the same methods for their determinations, 

 namely, that of determining the expansion of water in glass vessels (dilatometers). 

 Hagen employed the weighing process, but at high temperatures took no special pre- 

 cautions to prevent his fine wire becoming slightly wetted by the steam condensing 

 on its surface. This might account for his values at 90° and 100° falling below 

 mine || . 



As I shall have to speak of the above series after describing the experiments with 

 mercury, I will postpone the remarks I have to make. 



IV. On the Sedetermination of the Coefficient of Expansion of Mercury. 



The mercury employed for the following experiments was purified by treating the 

 commercial metal with nitric acid, distilling it, again treating it with nitric acid, redistil- 

 ling and keeping it till required for use under a solution of the protonitrate of mercury. 

 When required for use it was again treated with nitric acid on a water-bath for some 

 little time, thoroughly washed with distilled water, dried first on the water, and then 

 heated over the naked flame. 



To weigh the metal in water at different temperatures, small buckets (about 20 millims. 

 long, 15 millims. wide) were made from the ends of thin test-tubes. Across the mouths 

 of these a thin platinum wire was fused to serve as a handle, to which the very fine wire 

 can be fastened. 



• Pogg. Ann. xcii. 42. t Ann. de Chim. et de Phys. Ixx. (I"' serie) 1. 



+ Ann. de Chim. et de Phys. xv. (3"' serie) 325. Calculated by Fkanxenheim, Pogg. Ann. Ixxxvi. 451. 



§ Abhandlungen d. k. Akad. d. Wissensch. zu Berlin, 1855. 



li Henbici and Jolly's values (Bericht der k. bayer. Akad. derWissens. 1864, 1 Heft 11, p. 141) are not 

 quoted in the above Table, as they compared their thermometers with an air-thermometer, and do not give the 

 differences between them ; so their results are not comparable with those in the Table. I shall refer to this 

 point in my paper on the expansion by heat of metals and alloys. 



