378 



SCIENCE. 



[N. S. Vol. III. No. 63 



and to remove it as carbonic oxide. The 

 process is represented by the equation : 

 CaOH-3C=CaC,+CO. The carbide is ob- 

 tained as a melted mass with crystalline 

 structure, which when brought in contact 

 with water is transformed to slacked lime, 

 and to acetj'lene which is given off as a gas. 

 The formula for this transformation is : 

 CaC,+2Hp=Ca(0H),+C,H,. All the al- 

 kaline earths and alumina have been sub- 

 jected to the same treatment, and it has 

 been found that the carbides of barium, 

 strontium and calcium have similar formulse 

 and give off acetylene when treated with 

 water. The carbide of aluminum has the 

 formula : Al^Cs, and evolves marsh gas when 

 treated with water. It may be added that 

 a mixture of silica and carbon yields the 

 carbide of silicon, SiC. The compound is 

 formed when the two boches meet as va- 

 pors in the intense heat of the electric fur- 

 nace and combine as a sublimate of beauti- 

 ful crystals, now sold under the name of 

 Carborudum. The powdered crystals have 

 sharp cutting edges, hard enough to scratch 

 rubies, and consequently make an excellent 

 polishing and grinding material. 



It is to be noticed that this formation of 

 carbides affects the elements which make 

 up by far the larger part of the earth's 

 crust, so that from a geological as well as 

 a chemical point of view these newly dis- 

 covered transformations are of the utmost 

 importance. 



The reduction of these oxides to carbides 

 is only possible at the high temperature 

 of the electric furnace, and it is very in- 

 teresting to note that at three very different 

 stages of temperature we have such differ- 

 ent conditions presiding over the union of 

 the elements that each temperature corre. 

 sponds to a new chemistry. 



The temperature of the electric furnace, 

 which has been estimated to be from 3,500° 

 to 4,000° Cent., may be considered as inter- 

 mediate between the sun's temperature. 



estimated by different physicists at 5,000° 

 to 8,000°, and the temperatures of our 

 smelting furnaces, which range from 1,200° 

 to 1,500°. ]Srow, in the sun's atmosphere, 

 spectroscopic observations tell us that the 

 elements exist uncombined, and we can even 

 observe great masses of free oxygen in the 

 presence of heated hydrogen and of metals 

 so transformed in the properties which we 

 are accustomed to recognize that they do 

 not combine, but rise as vapors from the 

 hottest part of the sun, condense and fall 

 back in metallic clouds, which we know as 

 sun spots. Here, then, is a temperature 

 which is too hot for chemistry, if we define 

 chemistry as the science of the combination 

 of bodies. 



The next temperature on a descending 

 scale that we have access to is that of the 

 electric furnace ; here a partial combination 

 only is possible ; much of the oxj'gen re- 

 mains free ; carbon only burns to the non- 

 oxide of carbon, and the carbides and not 

 the oxides of the alkaline earths are the 

 stable forms of combination. 



Then, at a lower temperature the bright 

 red heat of our smelting furnaces, the same 

 carbides formed in the electric furnace, when 

 exposed to free oxygen or to air, burn to 

 oxides and to carbonic acid, and at a still 

 lower temperature these two unite to form 

 carbonates represented by the chalk and 

 magnesian limestone which make so large a 

 part of the earth's crust. Nature has so 

 adjusted her processes that a small residue 

 of oxj'gen remains, which, mixed with nitro- 

 gen, constitutes the vital air of our atmos- 

 phere. The carbides of aluminum and 

 silicon burn in a similar way with oxygen, 

 and the stable condition at any temperature 

 lower than a bright-red heat is that of sili- 

 cates and carbonates which make the chief 

 strata of the earth. 



The oxidation of carbides, which became 

 possible when our globe cooled down to a 

 red heat and solidified, has perhaps been a 



