172 cox. 



burning takes place in pure oxygon. In all older calorimeters this occurs slowly 

 under atmospheric pressure, while in a number of the more recent ones the explo- 

 sion method is used; that is, the combustion occurs under a pressure of fifteen to 

 twentj'-five atmospheres. Another method used in some of the calorimeters is to 

 effect combustion with combined oxygen. The explosion method is the one used 

 in the Berthelot ' bomb and lias the advantage over most of the other forms of 

 apparatus in that perfect combustion is attained.* In 1892, Mahler" employed an 

 enameled bomb and obtained results as satisfactory as with the platinrmi bomb of 

 Berthelot, while the cost of the apparatus is much less. In 1849, Hem pel ° intro- 

 duced the idea of pressing the wire into the coal briquette for electrical incineration 

 and in 1897 Krijker ' added to the bomb a head which was fitted with two gas-tight 

 valves, which greatly facilitates the determinntitm of the products of combustion. 

 Tliesa points are all included in the Berthelot-Mahler " bomb calorimeter which 



^ See bibliography. 



'Fries, J. A. (Journ. Am. Chem. 8oc. (1909), 31, 272), using an Atwood 

 bomb (which is a modifieation of that of Berthelot) with a modified top has 

 shown that the determination of carbon by means of it "is absolutely reliable 

 and gives very accurate results." 



= Mahler, P. Ztschr. f. angeir. GUem. (1892), 5, 491; (1898), 11, 865. 



"Hempel, W. Hid. (1892), 5, 389; Langbein, H. lUd. (1890), 9, 488. 



■Kriiker. lUd. (1898), 11, 865. 



' Calorimeter nach Berthelot-Mahler mit geanderter Einrichtung der Verbren- 

 nungsbombe (nach dem System von Dr. K. Kroker). Verfertiger, Julius Peters, 

 Berlin, X. W., Thurmstr. 4. This is an apparatus in which tlie combustibles are 

 burned in compressed oxygen in a vessel, called a "bomb," surrounded by a 

 large quantity of water, and tlie products of combustion cooled by the water 

 until the temperature is reduced to that of the water. Any water formed by 

 the combustion is condensed, and its latent heat is also given up to the calori- 

 meter. Corrections are made on the end temperature for the water value of 

 the appaiatus, for radiation and for the heat of formation of the products of 

 combustion, including the water formed, and the difference determined between 

 this result and the initial temperature. The increase in temperature is a 

 measure of the heat-producing power of the coal. The calorific value is the 

 product of the units of water by the degrees raised ; that is, the heat produced by 

 the burning of a unit weight of coal under these conditions. 



The most troublesome source of error in careful calorimetric work is the loss 

 or gain of heat by the calorimeter from its surroundings. Unavoidable ir- 

 regularities in the conditions make this correction variable and its determination 

 somewhat uncertain. Many methods of making it have been proposed. In the 

 experiments given in this paper this loss, which is mostly due to radiation, was 

 in the majority of cases taken into consideration according to the Regnault-Stoh- 

 mann-Pfaundler formula (Stohmann, Journ. f. prakt. Chem. (1889), N. F. 39, 

 517 et seq.) , that is: 



v—c' /t.—!, , i^+t,, , \u—l \ 



The corrections ^/ ^ I g i 2 ' ) (/) — nr I — (»— 1) 1.' where, 



i'=the mean temperature difference of the preliminary period. 

 .r=the mean of the temperature readings of the preliminary period. 

 *i> *2 • • • /n=the temperature readings of the combustion period. 



.i!'=the mean temperature difference of the period after combustion. 

 .r'=the mean of the temperature readings of the period after combustion. 

 «=:the number of the temperature readings of the combustion period. 



