Chemistry and Physics. 455 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Transformation of Carbon into Diamond. — It was shown 

 by Pepys, in 1815, that an iron wire heated to redness in contact 

 with diamond was converted into steel. Dr. Albert Ltjdttig now 

 claims that under great pressure in an atmosphere of hydrogen 

 this reaction is reversed, and also that carbon fused in the electric 

 arc in absence of iron, under the same conditions of pressure, is 

 likewise converted into diamond. In carrying out the experi- 

 ments, pressures as high as 3100 atmospheres were used, A spiral 

 of iron wire was embedded in powdered retort-carbon and heated 

 by an electric current in a highly compressed atmosphere of 

 hydrogen. In a few moments the resistance, ^vhich was slight at 

 first on account of the conductivity of the carbon, rose to that of 

 the iron spiral. This indicated that the carbon in contact with 

 the spiral had become non-conducting, and careful examination 

 showed that on some of the pieces of carbon were brilliant, minute 

 crystals, possessing the hardness, specific gravity, and refraction 

 of the diamond. The greater part of the carbon contained in the 

 iron spiral had also been converted into diamond. The crystals 

 had the characteristic irregular surface shown by the diamonds 

 produced by Moissan by the sudden cooling of molten iron. To 

 produce diamonds without the use of iron, it was found necessary 

 to use much higher temperatures and actuallv fuse the carbon 

 under very high pressure. Thus fused it was shown to be a non- 

 conductor, and hence was considered to be molten diamond. 

 Lender the pressure employed this fusion took place very easily 

 in the electric arc, and there were thus obtained spherical masses, 

 of the size of peas, having the great hardness and crystalline 

 structure of carbonado. It is the intention of the author to 

 develop the process for the commercial manufacture of diamonds. 

 — Chemik. Zeitg., xxv, 979. h. l. w. 



2. A7i lodometric Titration of Thiocyanic Add. — It has 

 been shown by Rupp and Schied that sulphocyanides are oxidized 

 in sodium bicarbonate solution, according to the equation, 



HSCN + 41, 4- 4Hp = H^SO^ + THI + CNI, 

 but starch cannot be used as an indicator in applying this reaction 

 on account of the presence of cyanogen iodide ; and, moreover, the 

 yellow color of the latter compound makes the method applicable 

 only to small quantities where the disappearance of the iodine 

 color is used. It has been found by Meinecke, however, that in 

 acid solutions the following reaction takes place: CNI + HI = l2 + 

 HCN. Thiel has now used the facts which have been stated for 

 devising a very convenient method for making this titration. 

 The thiocyanate is first treated with an excess of iodine solution 

 in the presence of sodium bicarbonate, enough water being used 

 to dissolve the latter. The reaction is complete in four hours at 



