

CHEMISTRY. (NEW PROCESSES.) 



115 



Dimethyl arsine, (CH 2 ) AsH, a substance hith- 

 erto unknown, has been obtained by Dr. Palmer, 

 of the University of Illinois, by the reduction of 

 cacodyl chloride. It condenses to a colorless, 

 mobile liquid boiling at 36 F. ; is endowed with 

 the characteristic cacodyl odor, and spontane- 

 ously inflames with some violence in contact 

 with the air. When air is admitted to the mix- 

 ture of its vapor with hydrogen a dense white 

 cloud is produced, which rapidly settles upon 

 the walls of the vessel in the form of a crystal- 

 ling deposit which is very soluble in water. 



Two remarkable substances, carbazide or car- 

 bonyl nitride, CON 6 , the nitrogen analogue of 

 phosgene gas, COC1 6 , and diurea, CO (NH.NH) 2 . 

 CO, the carbonyl derivative of hydrazine. are 

 described by Prof. Curtius and Herr Heiden- 

 reich. 



New Processes. By a modification of the 

 form first used in applying pressure in his ex- 

 periments, M. Moissan has been able to produce 

 artificial diamonds, which, though small, are 

 transparent and colorless like natural diamonds. 

 The former experiments were made with iron 

 and silver as solvents for the carbon, and the 

 mixture of metal and excess of charcoal was 

 heated in the arc of the electric furnace under 

 pressure until most of the charcoal was dissolved 

 in the white-hot metal, after which the hot 

 crucible was thrown into a tank of water to ef- 

 fect sudden cooling. Bismuth was afterward 

 tried as a solvent, but was not found suitable, 

 because a violent explosion took place when the 

 fused mass was projected into water. Iron is 

 therefore still used, and the cooling is effected 

 by pouring the contents of the crucible into a 

 bath of just melted lead. The solution of car- 

 bon in molten iron, being lighter than liquid 

 lead, rises to the surface in spherical globules ; 

 the smaller spheres solidify before reaching the 

 surface of the lead, but the larger ones are still 

 liquid and are still so hot that they cause the 

 lead at the surface to burn in contact with the 

 air. Upon removing the globules floating at 

 the surface of the lead, dissolving their leaden 

 coating in nitric acid, and subsequently remov- 

 ing the iron by solvents, the transparent dia- 

 monds are readily isolated. They possess the 

 same wonderful limpidity, high refractive power, 

 hardness, and density as native diamonds, and 

 exhibit many of the properties, such as anoma- 

 lous polarization and occasional spontaneous 

 disruption, which are characteristic of some 

 Cape diamonds. They scratch rubies, and resist 

 the action of a mixture of potassium chlorate 

 and fuming nitric acid, but burn in oxygen at a 

 temperature of about 900 C., with formation of 

 pure carbon dioxides. 



The separation of oxygen from the nitrogen 

 of the air has been practically effected by two 

 processes, both of which depend upon (1) the 

 formation of higher oxides of certain metals, and 

 <2) the elimination of the oxygen from the 

 higher oxides by the application of high tem- 

 peratures or of superheated steam. Oxygen is 

 thus obtained by the Brin process by exposing 

 ordinary heated baryta, BaO, to air that has 

 been freed from carbonic acid, whereby the per- 

 oxide, Ba0 2 , is formed ; and then driving off 

 the second part of oxygen by heat. In this 

 process the same baryta may be used over and 



over again indefinitely without any further 

 preparation. Another method of obtaining oxy- 

 gen from the air is by heating manganate of 

 potassium, KMn0 4 , in a current of steam, when 

 oxygen is evolved and the lower oxides of man- 

 ganese are formed. The caustic potash and the 

 reduced manganese are treated again in contact 

 with air, when manganate, due to absorption of 

 the oxygen of the air, is reformed. Another 

 method, more complex, but offering some advan- 

 tages, has been introduced by G. Kassner. In it 

 calcium plumbate, Ca 2 Pb0 4 ,' being exposed to 

 moist furnace gases, absorbs carbonic acid, and 

 is converted into a mixture of carbonate of lime 

 and free peroxide of lead. Then, on heating 

 this mixture, oxygen, at first pure, is evolved ; 

 but as the temperature rises it is contaminated 

 more or less by carbonic acid, which is readily 

 removed, however, by passing the gas over a 

 column of fresh plumbate. Toward the end of 

 the operation, which is assisted by means of a 

 current of superheated steam, carbonic-acid gas 

 in a state of purity is given off. The residue in 

 the retort, consisting of an intimate mixture of 

 lime and litharge, PbO., is reconverted into 

 plumbate simply by forcing a current of air 

 through the heated mixture in the retort. Thus 

 the plumbate can be used over and over again 

 in the same way that baryta and manganate are 

 iised in the other described processes. 



The separation of minerals of high specific 

 gravity has recently been greatly facilitated by 

 the introduction of the fused double nitrate of 

 silver and thallium, originally due to Dr. J. W. 

 Retgers. When these nitrates are brought to- 

 gether in the molecular proportion of 1 : 1 they 

 yield a double salt, which fuses at 75 C. to a 

 clear, mobile liquid, having a specific gravity of 

 about 5, and miscible with water in all propor- 

 tions at temperatures between its melting point 

 and 100 C. The melting point also diminishes 

 rapidly as water is added, going down to 50 or 

 60 C., and fusion and solubility pass uninter- 

 ruptedly into one another. We have thus at 

 our command for the separation of mineral par- 

 ticles a liquid far exceeding in specific gravity 

 any of the previously described heavy solutions, 

 which has the advantage of being practically 

 colorless, neutral, soluble in water, and of being 

 readily recovered from the aqueous solution by 

 simple evaporation of the water bath. Some 

 further hints on the use of this convenient me- 

 dium are given in the "American Journal of 

 Science " by Messrs. Penfield and Kreider. Sep- 

 arations may be made in test tubes heated in a 

 water bath. After a separation is completed 

 and the fusion cooled, the test tube is broken 

 and the solid cake is divided, when the heavier 

 and lighter portions may be obtained by dissolv- 

 ing the double salt. If fractional separations 

 are required, the fused salt may be placed in a 

 tube with a narrow neck at the bottom, into 

 which is ground a glass rod to serve as a stop- 

 cock. This apparatus slips inside of a test tube 

 to within a few millimetres of the bottom. The 

 whole is heated in a beaker of hot water, and 

 the liquid is stirred by means of a glass rod bent 

 into a semicircle at the bottom. Heavy parti- 

 cles are drawn off by raising the ground-glass 

 rod. Small particles getting caught in the 

 stopper can usually be ground out by twisting 



