348 R. Bunsen — Calorimetric Investigations. 



LIU. — Calorimetric Investigations ; by E. BuNSEN* 



2. The Determination of specific heat 

 The simplest way of obtaining tbe specific heat of a substance 

 is to determine once for all the amount of heat, expressed in 

 scale divisions, which one gram of water loses in cooling from 

 1° C. to 0° C, and to divide by the value W,c thus formed, the 

 quantity of heat "W, measured on the same scale, which one 

 gram of the substance loses for the same difference in tempera- 

 ture. If the weight of the substance is G, its temperature t, 

 the number of corrected divisions which the mercury thread of 

 the scale has advanced T, then the specific heat desired results 



from the equation S = ^ ^ - , - - . - (6) 



in which, for ^, the boiling point of water, corresponding to the 

 state of the barometer during the experiment, is to be taken. 



In order to communicate to substances the constant tempera- 

 ture t, use is made of the apparatus, fig. 4 (p. 173), which is drawn 

 to a scale of } of its real size. The tin vessel A, which is provi- 

 ded with a water guage, contains as much water as is necessary 

 in order that, by means of the small gas lamp underneath, a con- 

 tinual jet of steam of 12 hours duration may be produced. IM 

 steam enters through the rubber tube o, and the outer glass vessel 

 B into the rubber tube h, which communicates with an ordmaiy 

 condenser. Within the vessel B, which is filled with contnu- 

 ally renewed steam, is the heating vessel / in the form_ ol an 

 ordinary thin -walled test-tube whose upper opening is not 

 widened out but somewhat narrowed and cut off sharply. ^-^ 

 opening projects several millimeters above the rubber ^^P^^ 

 closing the outer vessel B. When the body to be wanned nas 

 remained in the vessel/ which is surrounded on all sides ov 

 steam, about one hour, then the whole apparatus, through wnic 

 the steam still flows, is held by means of the cork ring n ; the suu 

 closed mouth j9 is on the likewise closed mouth 6 (fig. 1) ^^ ^^ 

 snow-surrounded calorimeter, the stoppers are rapidly rem^J ' 

 while almost simultaneously, by tilting the heating appa^^ ^ 

 B, the heated body is allowed to fall into the water a, Hg ^j 

 The time consumed in falling amounts to only a very sro 

 fraction of a second, so that the cooling during the same m . 

 be considered as vanishingly small. • j n 



On the bottom of the inner vessel a, fig 1, is coBtainea^ 

 small, perfectly moistened plug of loose cotton wool, ^^'^^' 



* Translated for this Journal, with permission of the author, from Po^^jjjco.' 

 Annalen der Physik und Chemie, Bd. cxli, by Dr. G. E. Moore, of ban J^t^" 



