ARTIFICIAL DIAMONDS. 261 



of things then so obscure as to be thought hopeless, by dissolving in 

 the liquid under examination some solid substance which fused at a 

 temperature much above the critical point of the fluid. 



Sulphur, for example, melts at 111 Fahr., and is soluble in carbon 

 dioxide, a liquid whose boiling-point is 42. When such a solution 

 was vaporized it was found that the sulphur was not deposited, but 

 remained diffused in the atmosphere of dioxide vapor ; or, in other 

 words, the sulphur was dissolved in the gas. If the side of a tube con- 

 taining such a gaseous solution of sulphur is approached by a red-hot 

 iron, the part next the source of heat becomes coated with a crystalline 

 deposit, which redissolves into the gas on the removal of the heat. In 

 the course of his experiments on the solubility of solids in gases Mr. 

 Hannay further noticed that many bodies, such as alumina and silica, 

 which, like carbon, are insoluble in water, dissolved to a considerable 

 extent in " water-gas," or water at the critical point when it is neither 

 a true liquid nor a true gas. This fact suggested to him that a solvent 

 might even be found for the hitherto insoluble element, carbon ; and, 

 as gaseous solutions were found to yield crystalline solids in almost 

 every case upon the withdrawal or dilution of the solvent gas, it was 

 hoped that, from such a gaseous solution of carbon, crystals of diamond 

 might be obtained. 



After a large number of experiments, however, it was found that 

 neither charcoal, lampblack, nor black-lead would dissolve in the most 

 probable solvents when these were brought to their critical points, and 

 a new road out of the difficulty had accordingly to be sought. 



Chemists have long known that what is called the "nascent" state 

 of matter is one very favorable to chemical combination. Thus nitro- 

 gen, for example, refuses to combine with hydrogen, but, if these two 

 substances are simultaneously liberated from some previous combina- 

 tion, they unite at the moment of birth with the utmost ease. Bearing 

 this in mind, it was ascertained that, when a gas containing both car- 

 bon and hydrogen is heated under pressure in presence of a metal, the 

 hydrogen is attracted by the metal and the carbon left free. 



Mr. Hannay attacked this nascent carbon with many gaseous sol- 

 vents, and it is his triumph to have found what he sought. In doing 

 so, he has removed a reproach of long standing from the science of 

 chemistry ; for, whereas the larger part of that science is occupied with 

 the chemistry of carbon and its compounds, this element has never 

 previously been either dissolved or vaporized by man. 



What the solvent is, we are not at present definitely told ; we only 

 know that it is some nitrogen compound, probably a cyanide ; but the 

 process is quite intelligible in the absence of this information, while 

 its products are open to the examination of experts. 



A hydrocarbon vapor, such as petroleum, is decomposed at a high 

 temperature and under great pressure. As the hydrogen and carbon 

 part company, the former is absorbed, while the latter, being nascent, 



