466 Scientific Intelligence. 



— 76°. When mixed with ether, the dioxide had a temperature 

 of —77° in air and of —103° in a vacuum. Liquid carbon diox- 

 ide solidifies in such a mixture. On the addition of the solid 

 dioxide to the ether it at first dissolves, and after a time bubbles 

 of gas are evolved. On continuing to add the dioxide the liquid 

 becomes saturated and opalescent, the temperature falling until 

 the instant of saturation is reached, when no farther fall of tem- 

 perature occurs on adding more dioxide. Hence it would appear 

 that the effect of the ether is due simply to its dissolving the di- 

 oxide. Other solvents may be used. Methyl chloride gives 



— 82°; sulphurous oxide —82°; amyl acetate —78°; phospho- 

 rous chloride —76°; alcohol —72°; and ethylene chloride —60°, 

 When the mixture with methyl chloride or sulphurous oxide is 

 placed in a vacuum the temperature is lowered to a point at 

 which the solvent solidifies and then no farther reduction takes 

 place. The temperature thus obtained with methyl chloride is 



— 106°. A mixture with chloroform solidified at the ordinary 

 pressure at —77°. — C. JR., cvi, 1631; J. Chera. Soc., liv* 1025, 

 Oct., 1888. G. F. B. 



- 3. On the Determination of the Heat of Combustion of Coal. 

 — Scheurer-Kestner has analyzed and has also determined the 

 heat of combustion of twenty-one samples of coal from the north 

 of France, by direct experiment, and has compared the results 

 with those calculated from the composition of the coals. The 

 coal in small fragments was burned in a rapid current of moist 

 oxygen in a Favre and Silbermann's calorimeter ; the results being 

 corrected by subtracting from the heat of combustion actually ob- 

 served with the moist gas, and consequently with complete con- 

 densation of the water formed, the number of calories equiva- 

 lent to this condensation. Since the combustion of hydrogen 

 gives 34,500 or 29,088 calories according as the water formed is 

 condensed or is in the state of vapor, the difference, or 5413 ca- 

 lories, multiplied by the content of the coal in hydrogen, repre- 

 sents the number of calories to be subtracted from the observed 

 heat of combustion. The values of the heats of combustion ac- 

 tually obtained do not agree with the values calculated from the 

 composition, being sometimes greater than the sum of the heats 

 of combustion of the constituents and sometimes less. Cornut 

 has proposed a formula for calculation based on the assumption 

 that while solid carbon evolves 8080 calories*, the heat of com- 

 bustion of carbon in the state of vapor is 11,214 calories. But 

 the calculations founded on this formula of Cornut, while giv- 

 ing results somewhat closer to those actually observed in some 

 cases, are in other cases so far from the truth as to destroy confidence 

 in it. The formula of Dulong is even less satisfactory. No explana- 

 tion is offered as to the cause of these discrepant results, but they 

 seem to establish the important fact that coal has been formed at 

 least in part by endothermic reactions. The general results give 

 between 8340 and 9257 calories, the mean values lying between 

 8400 and 8800 calories. — Ann. Chirn. Phys., VI, xv, 262, Oct., 

 1888. J. Chem. Soc., liv, 774, Aug., 1888. G. r. b. 



