Chemistry and Physics. 221 



SCIENTIFIC INTELLIGENCE 



I. Chemistry and Physics. 



1. A Misconception of Critical Temperature. — In a discourse 

 recently delivered at the Royal Institution in London, in regard 

 to ore deposits and their distribution and depth, Professor John 

 W. Gregory presents an astonishing view of the condition of 

 water at temperatures above its critical point. It is evidently 

 his opinion that the elements of water are not combined with 

 each other above the critical temperature of liquefaction, for he 

 says : 



" Water, although its constituents may come from vast depths 

 within the interior, is limited to a depth of perhaps only six or 

 seven times the depth of existing mines. The lower limit is due 



to the internal heat of the globe Now water cannot 



exist at a temperature higher than its critical point, 687° F. . . . 

 At depths below about 37,000 feet the temperature would be 

 above the critical point of water, which therefore could not 

 exist as such. Its elements would be given forth as separate 

 gases from the slowly cooling magma ; the gases would rise, and 

 having passed into a zone with a temperature below the critical 

 would combine to form water." 



The author has confused the critical temperature of liquefac- 

 tion, 358° C, with the temperature of dissociation of water, 

 which is probably about 2500° C. The only change which water 

 undergoes at its critical temperature is the loss of its surface 

 where it is in contact with a gas or vapor, no matter how great 

 the pressure may be. If the view set forth in the quoted 

 extract were true, the maximum temperature to be obtained 

 by the combustion of hydrogen and oxygen would be 687° F., 

 which is near the boiling point of mercury. — Chem. JVeics, 

 xciv, 143. h. l. w. 



2. New Determination of Free Sulphur. — In view of the fact 

 that the methods in vogue for the oxidation of free sulphur in 

 the wet way, such as treatment with hydrochloric acid and potas- 

 sium chlorate, are long and difficult, even with very finely divided 

 sulphur, E. Berger proposes to use for this purpose fuming 

 nitric acid to which a little potassium bromide is added. The 

 bromine set free dissolves the sulphur and the resulting bromide 

 of sulphur is decomposed at once by the excess of acid. The 

 reagent acts in the cold, in a few minutes, even when the sulphur 

 is in the form of small crystals, and the result of the action is 

 sulphuric acid. To carry out an analysis, the substance contain- 

 ing *1 or '2 s of sulphur is weighed out in a small capsule, 10 cc of 

 fuming nitric acid are put in, and then -5 to I s of pure potassium 

 bromide. After a few minutes the capsule is placed on the 



