SCIENCE 



NEW YORK, SEPTEMBER 15. 1893. 

 "CARBORUNDUM"; A SILICIDE OF CARBON. 



BY WILLIAM K. BLAKE, NEW HAVEN, CONN., AND SHULLS- 

 BDEG, WIS. 



Under the name "carborundum," a new compound of 

 carbon and silicon has been commercially introduced as 

 an abrasive ; a substitute for emery and corundum. It is 

 a very hard crystalline solid, of a deep green color, and 

 was obtained about the year 1890 by Mr. E. Gr. Acheson, 

 of Chicago, while experimenting with the electric furnace 

 with the intent of producing artificial diamonds. Under 

 the supposition that he had obtained a compound of car- 

 bon and alumina he gave it the name "carborundum." 

 Analysis,* however, shows the following composition : 

 Si - - - - 69.10 

 C. - - - - - 30.20 

 Al.Oj and Fe, O^ - 0.49 



CaO - - - - 0.15 

 A^Tiich may be expressed by the formula SiC ; the other 

 substances being regarded as imjjurities, and as impart- 

 ing the color, which is found to be variable, from nearly 

 white to a deep green and blue. 



At a session of the Academy of Sciences of France, May 

 16, 1892, M. P. Schiitzenberger described the production 

 of a new compound with the same formula, f It appears, 

 however, that some carborundum had previously been 

 molded into buttons and mounted in bulbs for electric 

 lighting and exhibited by Mr. Nikola Tesla before the In- 

 stitution of Electrical Engineers in London in the month 

 of February, 1892, but its composition was not then 

 known. 



The value of this substance as an abrasive has led to its 

 manufacture uiDon a large scale, and its introduction in 

 the form of powders of different degrees of fineness, and 

 of wheels and whetstones and polishing cloths. 



The processes of manufacture are described in the 

 memoir cited and also in another by the inventor,J which 

 gives illustrations of the furnace, which consists merely of 

 a rectangular box, about sis feet long, eighteen inches 

 wide and a foot deep, built up of fire brick, in which a 

 mixture of sand and carbon is exposed to the electric 

 current for eight hours. The result is a mass of crystals 

 of small size, which is crushed, and the powder is digested 

 with dilute sulphuric acid to remove impurities. 



The crystallization has been carefully studied by Prof. 

 B. W. Frazier, of Lehigh Univ., who finds it to be rhombo- 

 hedral, and in some cases hexagonal. Both direct and 

 inverse rhombohedra were observed and determined, viz. : 

 i-S. 4-5, lo-ii, 1, 5-4, 4-3, 10-7, 2, 5-2, 4, 19-4, 5, 10.|1 

 In some crystals the direct and inverse rhombohedra of 

 the same parameters were found on the same crystal, so as 



to impart to it an appearance of holohedral hexagonal 

 symmetry. 



The value for the length of the vertical axis is given as, 

 G = 1.2264. 



In the crystals which I have examined the tabular habit 

 prevails, and as seen under the microscope they consist 

 of hexagonal plates with the rhombohedral planes too 

 small to permit of their inclination being measured.^ 



The specific gravity of a bluish-green colored mass as 

 determined by myself at 60 F. was found to be 2.546. 

 Prof. J. W. Richards found it to be for the green crystals 

 3.123, and for the blue somewhat less. 



The hardness, which is the most important character 

 industrially, lies between the sapphire and the diamond, 

 and may thus be expressed by 9^. It is claimed by the 

 inventor that the powder on a rapidly revolving lap will 

 cut and polish the diamond, and he believes that it may 

 be advantageously substituted for diamond dust in dia- 

 mond cutting. 



It is a good conductor of heat, and is not fusible before 

 the blow-pipe. It also resists all acids, even the fluoric, 

 and does not burn when heated in a current of oxygen ; 

 this being one of the methods adopted to obtain it free 

 of any graphitic carbon. 



The color and lustre are remarkably brilliant, and if by 

 any modification of the process large and solid crystals 

 can be made, we shall have a valuable addition to our list 

 of gems. 



Considering the abundance of these two elements in 

 nature, both silicon and carbon, and the comparatively in- 

 destructible nature of the compound formed by their 

 union, it is surprising that we do not find this compound 

 in nature. Its absence indicates the prevalence of condi- 

 tions during the formation of the crust of the earth un- 

 like those of the electric furnace. 



* Bv Dr. Mulhaeuser, chemist of the Carborundum Company, in Memoir 

 by E. G. Acheson : " Carborundum, Its History, Manufacture and Uses.'' 

 Jour. Frank. Inst., Philadelphia, Pa., Sept., 1S93. 



t Contribution to the History of Carbo-silicious Compounds. 



X Carborundum, etc., The Electrical Engineer, XV., p. 227, March, 1893. 



I From a Report to the Carborundum Co., Memoir cited. Appendix, p. 19. 



LATTER-DAY TAXIDERMY. 



BY VERNON L. KELLOGG, ITHACA, N. Y. 



Taxidermy is hardly recognized as one of the fine arts, 

 yet. Perhaps it may never be. But the truthfulness of 

 representation, and the artistic effects of posing and 

 grouping which "mounted" animals may exhibit, can often 

 invest such work with an interest for those who may not 

 be much inclined toward taxidermy for the sake of the 

 skin-preserving. The displays of mounted birds and 

 mammals at the World's Fair present several stages of pro- 

 gress in the art of taxidermy, and lead one to speculate 

 on the outcome of it all. For scientific purposes, sensu 

 stricta, the making of bii-dskins is probably preferable to 

 attempting the mounting of the specimens ; and so per- 

 haps with many of the mammals. Evidently, however, if 

 the specimen in hand can be truthfully rejiresented so 

 far as form and characteristic position and externals go, 

 it may serve as a teaching object to many to whom the 

 " made " skin, with accompanying written measurements, 

 may be without a lesson. 



But it seems as if it were possible to go even farther : 



t Vide Article in Eng. Min. Jour., Sept., 1893. 



