Chemistry and Physics. 477 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Dissociation of Hydrogen into Atoms. — It has been 

 found by Irving Langmuir that at extremely high temperatures 

 the power consumption necessary to maintain a tungsten wire at 

 a given temperature in hydrogen gas increases with abnormal 

 rapidity with the temperature. This rapid increase in loss of 

 heat could not be explained by simple convection or conduction, 

 and the most probable explanation appeared to be that dissocia- 

 tion of the hydrogen molecules (H 2 ) into atoms was taking place. 

 This dissociation in the region close to the hot wire would 

 absorb large quantities of energy, the hydrogen atoms would 

 then diffuse out into the gas at some distance from the wire and 

 would then recombine and give out the heat of the reaction, thus 

 causing an abnormally high heat conductivity. This view is 

 strengthened by the fact that Magnanini and Malagnini have 

 observed that the heat conductivity of nitrogen peroxide is three 

 times as great with the partly dissociated gas as when it is com- 

 pletely dissociated. Langmuir has made this explanation still 

 more probable by calculating the energy loss from heated wires 

 by means of simple equations and finding that the calculations 

 agree well with the experimental results in the cases of nitrogen 

 gas and mercury vapor up to 3500° C. (abs.), and also in the 

 cases of carbon dioxide and air up to the melting-point of plati- 

 num, while in the case of hydrogen there is agreement only up 

 to about 2100° C. (abs.), and above that point the energy loss 

 increases very rapidly until at 3300° it is four or five times as 

 great as the calculated value. It was shown by experiments that 

 the' phenomenon is an actual dissociation which follows the law 

 of mass action, and that the volume of the dissociation products 

 is approximately twice the volume of the original hydrogen, as 

 the equation H 2 = 2H requires. The heat of this reaction was 

 found to be 550,000 joules, or 130,000 calories at constant vol- 

 ume. The extent of the dissociation at atmospheric pressure was 

 calculated to be such that the partial pressure of the atomic 

 hydrogen at 3300° C. (abs.) is two-thirds of the total pressure. — 

 Jour. Amer. Chem. Soc, xxxiv, 860. H. L. w. 



2. The Determination of Sulphur in Pyrites. — This important 

 determination has given much trouble to analytical chemists in 

 the past, and it has been the subject of many investigations. 

 Allen and Bishop have now devised and have carefully tested 

 a new method for this purpose, which gives constant and accu- 

 rate results, and which promises to supersede the older methods. 

 The main features of the process consist in decomposing the 

 substance with a mixture of liquid bromine and carbon tetra- 

 chloride with subsequent addition of strong nitric acid, the 



