R. Bunsen—Calorimetric Investigm 



Aet. XXYL—Cahnmeirk Investigations ; by R BUJTSEN * 



1. The Ice Calorimeter. 

 The calorimetric methods hitherto in use are attended vitb 

 the disadvantage that proportionately large quantities of tlie 

 calorimetric fluid, as well as of the substance under investiga- 

 tion, must be employed, in order that the loss of heat which 

 unavoidably attends the measurements may be so reduced that 

 all corrections therefor may be small in comparison witn the 

 amount of heat to be measured. In the determination ot 

 specific heat, especially when the more exact of the methods 

 previously in use are employed, satisfactory resuhs can hardly 

 be anticipated when the amount of material used in the expen- 

 ments is less than from 10 to 40 grams. The preparation ot 

 the rarer substances, in a state of absolute purity, in such qi^- 

 titles often presents almost unsurmountable difficulties, and n 

 is perhaps only on this account conceivable that we are no 

 acquainted with the specific heats even of all the element 

 which have been isolated in a state of purity, although tlie&e 

 determinations are of fundamental importance for the establisfi- 

 ment of the atomic weights. . i 



The instrument described in the following pages is/^sign^ 

 to aid in overcoming this disadvantage. It is based on ttt 

 principle of measuring the amount of ice melted by the «of ^J^; 

 nicated heat by means of the diminution in volume which tub 

 ice undergoes on melting. 



The instrument, fig. 1, which was made at the glass blo^ver^ 

 lamp, consists of an inner glass vessel, a, having the form oi a 

 ordinary test tube and melted into the cylindrical glass case • 

 From this case b issues the glass tube c, to whose upper e ^ 

 tremity the iron head-piece d is cemented. The inner ves^el 

 is filled fi-om « to /., tlie outer case b from p to A, with pre ^ 

 ously boiled water; the remainder of the case b together ^^^ 

 the tube c, is filled up to the height y with previously bou*^^ 

 mercury. In order to arrange the apparatus for use, 3; cjhn ^ 

 of ice enclosing the entire vessel a is produced in the case ^ 

 the whole apparatus is then surrounded with snow m a m 

 vessel, and the calibrated scale tube s, which has been cement^ 

 into the cork with fine sealing-wax, is screwed down throng 

 the mercury of the head-piece d very tight into the opening 

 the tube c, whereby the scale tube fills itself with mercury. ^ 

 order that the pressing in of the stopper may be unattenatj^ 

 with danger for the rather fragile apparatus, the instrument 

 18 JoHraal, with permission of the author, from PogfffV 

 und Chemie, Bd. CXLI, S. 1, by Dr. G. B. Moobe, " 



