540 Royal Society : — 



acid and thus identified with the other forms of carbon, but having 

 a distinct atomic weight, namely 33 (H=l). 



After the detail of certain experiments by which the author was 

 led to believe in the existence of a distinct system of compounds of 

 graphite, an account is given of a peculiar crystalline substance 

 formed bv the prolonged oxidation of graphite. This substance 

 consists of transparent plates of a pale yellow colour, which exhibit 

 under the microscope an appearance distinctly crystalline. The ana- 

 lysis of this substance gave for its formula Cn H; 0, (C= 12, 0= 16). 

 From the ratio of the hydrogen to the oxygen in this substance, 

 from the circumstance that it is procured from graphite alone, and 

 from its general physical properties, it is inferred that this substance 

 is the term in the system of graphite which corresponds to the 

 compound of silicon, oxygen and hydrogen, in the system of silicon, 

 procured by Wohler from the graphitoidal form of that element, 

 and to which Wohler has assigned the formula Si^H, Oj (Si=21). 

 If it be assumed that this conclusion is correct, the further in- 

 ference is that the bodies are similarly constituted. On this hy- 

 pothesis, to arrive at the atomic weight of graphite, the total 

 weight of carbon, 132, is to be divided by 4, which gives the 

 number 33 ; and for the formula of the body, putting Gr=33, we 

 have Gr, H,0,. 



This conclusion is confirmed in a remarkable manner by the spe- 

 cific heat of graphite. The specific heat of the elemental bodies 

 varies inversely with their atomic weight. This law is so well 

 established, that Regnault has even proposed to determine the 

 atomic weight by it exclusively. There are, at any rate, only two 

 numbers which can be assigned as the product of the specific heat 

 into the atomic weight of the elemental bodies, namely, approxi- 

 mately the numbers 3'3 and 6*6. But to this law there is one sin- 

 gular exception. Carbon in all its forms is anomalous. The specific 

 heats of diamond, graphite, and wood-charcoal are each different, 

 and taking the atomic weight of carbon as 6 or 12, no one is accord- 

 ant with the law. The specific heat of graphite is 0' 20 18 7. Now, 

 taking the atomic weight of graphite as 33, we have 33X'201 = 6*63, 

 a result in accordance with the law. The inference is, that the asser- 

 tion that 33 is the atomic weight of graphite is not only a convenient 

 expression of chemical analysis, but corresponds to a physical fact. 



May 19. — Major- General Sabine, R.A., Treas. andV.P., in the Chair. 



The following communications were read : — 



"On the Specific Gravity of Alloys." By A. Matthiessen, Ph.D. 



Before commencing a research into the electric conductivity of 

 alloys, the author deemed it requisite, as a preliminary step, to 

 determine their specific gravities ; and the methods employed and 

 results obtained in this inquiry are given in the present paper. 



The metals used were antimony, tin, cadmium, bismuth, silver, 

 lead, mercury, and gold. The silver and gold were obtained in a 

 state of purity from the refiners, the other metals were purified by 

 methods which are described. The quantity prepared of each alloy 



