CARBON. 77 



Erdmann and Marchand's figures for natural graphite give the follow- 

 ing results : 



I-5376 gim. gave 5.6367 grm. CO.. 2.6659 

 1.6494 " 6.0384 " 2.6609 



1-4505 " 5-31575 " 2.6647 



In one experiment 1.8935 grm. of artificial graphite gave 6.9355 grm. 

 COj. Ratio for 0, 2.6628. This, combined with the foregoing series, 

 gives a mean of 2.6636, ± .0007. 



With the diamond they found : 



.0009 



In more recent 3'ears the ratio under consideration has been careful!}^ 

 redetermined by Roscoe, by Friedel, and by Van der Plaats. Roscoe* 

 made use of transparent Cape diamonds, and in a sixth experiment he 

 burned carbonado. The combustions were effected in a platinum boat, 

 contained in a tube of glazed Berlin porcelain ; and in each case the ash 

 was weighed and its weight deducted from that of the diamond. The 

 results were as follows, with the ratios stated as in the preceding series : 



1.2820 grm. C gave 4.7006 COj. 2.6666 



.0006 



Friedel's work,t also upon Cape diamond, was in all essential ])ar- 

 ticulars like Roscoe's. The data, after deduction of asb, were as follows : 



.4705 grm. C gave 1. 7208 CO.^. 2.6628 



.8616 " 3.1577 " 2.6640 



Mean, 2.6634, i .0004 



By Van der Plaats X we have six experiments, numbers one to three 

 on graphite, numbers four and five on sugar charcoal, and number six 

 on charcoal made from purified filter paper. Each variety of cai'bon 

 was submitted to elaborate processes of purification, and all weights were 



*Ann. Chim. Phys. (5), 26, 136. Zeit. Anal. Chem., 22, 306. 1883. Compt. Rend., 94, iiSo. 1882. 

 tBuU. Soc. Chim., 42, 100, 1SS4. 

 X Corapt. Rend., 100, 52. 1S85. 



