CAPACITY FOR HEAT OF METALS AT DIFFERENT TEMPERATURES. 139 



Tim mercury drawn into the Bunsen was directly determined from the loss in weight 

 of a small capsule ; in the first experiment, 27347 gr. of mercury ; in the second 

 experiment, 27335 gr. of mercury. 



The constant assumed was 15'44 mgr. mercury per calorie. 



The resulting value of the mean specific heat for this paraffin was 0"491, its density 

 l>eing 0'818. 



The mean specific heat of glass was determined in a similar manner and was found 

 to be 0'194. 



The specific heat and temperature variation of the hydrocarbon oil had already l)een 

 determined ('Phil. Trans.,' vol. 186, p. 338), viz., S, = 0'466 + 0'0009, its density 

 being 0"865. As both oils were paraffins, the temperature coefficients were assumed 

 to lie the same, to a first approximation. 



2. Alloy and Solder. 



The alloy-fixed lid was used only in our earlier experiments and when determining 

 the specific heats of certain metals at C. 



The mean specific heat of this alloy over the range C. to 47 '6 C. (its melting 

 point being 97 C.) was also ascertained by the Bunsen calorimeter and was found to 

 be G'0348. 



The soldered lid was used over the range C. to 125 C., hence, both its specific 

 heat and its temperature variations were required. 



A block of the sample of solder (3 kgr.) was cast and machined to the same size as 

 the other metal blocks. Its specific heat at C. and 97 C. was determined in our 

 apparatus in the same manner as copper, &c., 



S, = 0*0422 + 0-000038*. 



On analysis, the composition of the block was found to be 537 per cent, tin and 

 46'0 per cent, lead, with bismuth and antimony as impurities. The density of the 

 solder block was 8 "7 7. The platinum deposit on the ends of the quartz tubes was 

 negligible, the weight of three coats being only 0"0105 gr. 



3. Heat Absorbed by the Supporting Quartz Tubes. 



As previously indicated, two different copper lids were used. The copper alone in 

 the first weighed 51 "6 gr. and thin quartz tubes were fixed into its ferrules (which 

 were 15 mm. in depth) by fusible alloy. The copper alone in the second lid weighed 

 68 "5 gr. ; the tubes were of much heavier make and fixed with solder. The masses 

 of the quartz tubes per unit length in the first lid were only three-fifths of those 

 used in the second ; advantage was taken of this difference to determine the effective 

 capacity for heat of that portion of the quartz which might be regarded as rising 

 through the same range as the block of metal 



T 2 



