486 EEPOET— 1888. 



J. Bosscha gives' a formula c=l + '00022 (i — 18) as giving more 

 accurate values, as he thinks, for the specific heat of water at various 

 temperatures than Regnault's. 



Neesen - found, as some other observers before him had found, that the 

 specific heat of water diminishes from 0° up to a temperature as to which 

 they are not agreed, and increases after that temperature. If this is so 

 it is an exception to the otherwise almost invariable rule of increase of 

 specific heat with rise of temperature. 



According to some recent experiments by Cardani and Tomasini ^ the 

 mean specific heat of liquid water below 0° diminishes with rise of tem- 

 perature, being, e.g., '985 between— 10'67° and 0°, and -953 between 

 -6-52° and 0^ 



In a paper by Professor Rowland on the mechanical equivalent of heat, 

 presented to the American Academy of Arts and Sciences, June 11, 1879, 

 the author shows how, by assuming the axiom that the heat equivalent 

 to a definite quantity of energy is definite and constant, and repeating 

 Joule's experiments, using a large range of temperature of the water in 

 the calorimeter, the heat-capacity of water between two temperatures 

 can be determined so as to enable the specific heats at various tempera- 

 tures within those limits to be known, approximately. By this method, 

 as also by the method of mixtures, referring the temperatures to Sir W. 

 Thomson's absolute scale, Rowland was able to deduce the conclusion 

 that the specific heat of water decreases through 4° to about 30° to 35" ; 

 a temperature at which it is a minimum, and above which the specific 

 heat of water as usual increases with rise of temperature without change 

 of the state of the water. 



Carbon Compounds — De Heen. 



Several organic compounds, organic acids and salts of organic acids in 

 particular, gave, as found by P. de Heen,< specific heats which varied con- 

 siderably with the temperature below 100° ; this may possibly be due to 

 the temperatures being too high in these cases — or in most of them — to 

 give specific heats corresponding to the truly solid condition as suggested 

 by H. Kopp,^ the body being more or less softened by the heat. A similar 

 caution had been mentioned by Regnault, who looked upon a fortion of 

 the latent heat of fusion as being added to the true specific heat in many 

 cases, and in part accounting for the deviation of specific heats from the 

 law of atomic heats. It was on account of an incipient softening effect 

 of heat near 90° on the ' vitreous ' modification of selenion^ that Regnault 

 compared the specific heat of this modification with that of ' metallic ' 

 selenion at low temperatures, e.g. — 20°. 



Other Specific Heats. 



Naccari^ gives a formula y=a(l + ?/i) for the specific heat at tem- 

 peratures from 0° to over 200° for the metals copper, antimony, silver, 

 cadmium, aluminium, lead, zinc, nickel, and iron ; as an example, 



' Poffff. Ann. 1874 ; Juhelhd. 549. - Wwd. Ann. 2, 18, 1883, p. 369. 



= Naovo Cimento (3), 21, 185; C. S. J. Ahs. 1888, p. 102. 

 * Bull. Acad. Roy. Belg. (3), 5, 1883, p. 757 ; Ber. 16, 1883, p. 2655. 

 5 Ber. 19, 1886, p. 817. « Ann. Chim. 3, 46, 1856, p. 286. 



' R. Ace. di Torino, 23, 1887, p. 22; and Beibl. 12, 1888, p. 326. 



