1S4 Iltdett, Mack and Smyth — The Moisture Content. 



The coals here reported on cover the range of our 

 Important coals. The more mature coals corresponding 

 to the New River type are easy to handle. We may 

 safely use temperatures up to 300° before there is a 

 noticeable rate of decomposition of coal substances. 

 With the Pittsburgh type of coal a noticeable rate of 

 decomposition begins at a lower temperature, and the 

 amount of decomposition increases more rapidly with 

 increasing temperature. With still newer types these 

 tendencies begin at progressively lower temperatures 

 and are more marked. Preliminary work with lignites 

 and cellulose materials even more strongly emphasize 

 this tendency. 



This seems to be clearly in line with the view expressed 

 in the previous article on the genesis of coal. Starting 

 with woody material or peat, the various substances are 

 undergoing normal chemical reactions at ordinary tem- 

 peratures, not on account of the pressure of superim- 

 posed materials, but in spite of it. The rate of these 

 reactions are so slow that measurable results appear only 

 in geologic periods, but even these slow reaction veloci- 

 ties are of different orders of magnitude and evidently 

 the cellulosic substances largely disappear, while the 

 resinous and other substances with slower reaction 

 velocities have only partially run their courses. 



The volume of gases evolved with the moisture, taken 

 from the curves figs. 5, 6, 7, 8, are given in the table. 

 Here again the values are for our 60-mesh samples. 

 Probably the loss of gases in preparing these samples is 

 proportionally greater than that of the water. It will 

 be of considerable interest to know the real amount of 

 these gases in various types of coal and also their compo- 

 sition. From the work of Taylor and Porter (1. c), coals 

 heated to 250° in a vacuum for several hours give gases 

 which were mostly C0 2 (40-70%), with some 10% of 

 CO, a little methane, and traces of other hydrocarbons. 

 Some coals are known to liberate considerable quantities 

 of methane at ordinary temperatures. More exact infor- 

 mation on this subject would be of interest. 



Laboratory of Physical Chemistry, Princeton, N. J., June, 1917. 



