﻿Prof. R. Bunsen's Calorimeiric Researches, 1 75 



current of steam ; it is in the form of a common thin glass test- 

 tube, the top of which, however, is slightly narrowed and sharply 

 cut off. The mouth projects some millimetres above the india- 

 rubber stopper which closes the outer vessel (B). When the 

 substance has been heated for about an hour in the vessel (/), 

 the whole apparatus (which is supported on the ring of cork, ri), 

 with the mouth (p) still closed and the steam still passing 

 through, is brought near the similarly closed tube (8, fig. 1) of 

 the calorimeter surrounded with snow. The stopper of the 

 vessel / is quickly withdrawn, and at the same moment the 

 vessel B is inverted and the heated substance thus allowed to 

 drop into the water (a, fig. 1). The time occupied in falling 

 amounts only to a very small fraction of a second, so that the 

 cooling during this time is too small to be considered. 



At the bottom of the inner vessel («, fig. 1) a small loose and 

 thoroughly moistened piece of cotton-wool is placed, which is 

 prevented from rising np by being wound round a piece of 

 platinum wire. This cotton-wool serves two purposes : first, 

 it prevents the breaking of the tube when heavy bodies are dropped 

 into it ; and, secondly, it serves to remove the substances which 

 have been examined from the apparatus. For this purpose a 

 platinum wire suitably bent at the point is pushed into the cotton- 

 wool, which by this means is drawn up to the mouth of the tube ; 

 the substance lying on it is then removed, and the cotton-wool, 

 without ever being removed from the tube, is restored to its ori- 

 ginal place. 



The chief advantage which the instrument described possesses 

 over all other calorimetric arrangements, not to mention its 

 great sensitiveness, consists in the fact that all the heat which 

 the body gives up is employed to melt ice. The weight of sub- 

 stance which is placed in the water of the vessel a, fig. 1, at 0° C. 

 is so small compared with the weight of the water itself, that 

 the temperature never reaches 4° C. Since water at this tem- 

 perature possesses its maximum density, the heated liquid at the 

 bottom of the vessel a can never rise, and is protected from the 

 loss of heat not needed for the melting of the ice by a column 

 of water lying above it at a temperature of 0° C. whose power of 

 conducting heat is indefinitely small. 



This process is very nicely seen in the ice cylinder when it 

 has been used for thirty or forty determinations, when there is 

 found, quite at the bottom of the vessel a, a hollow space filled 

 with water, which very generally has the form of a little digesting- 

 flask, while the ice cylinder in the whole space above appears 

 quite unaffected. The weight of the substance to be examined 

 need not exceed 0*3 or at most 4 grms., according to the great- 

 ness of the specific heat to be expected. If the substance is fluid, 



