338 



SCIENCE. 



[N. S. Vol. XXIII. No. 583. 



In Watt's 'Dictionary of Chemistry' 

 platinum black is mentioned as a reagent 

 which produces this reaction, but since a 

 hot copper spiral is usually used in the 

 qualitative method of determining the pres- 

 ence of methyl alcohol, we call attention to 

 this reaction. 



The Use of Porcelain Dishes in Silicate 



Analyses: F. L. Kobtright. 



Platinum dishes are usually preferred 

 for evaporations in silicate analyses, on the 

 assumption that porcelain dishes are liable 

 to be corroded and thus an excess of silica 

 obtained. In a few cases where a loss of 

 silica is assumed to occur through the use 

 of porcelain dishes, the statement is made 

 that the loss occurs through not being able 

 to see the silica adhering to the white sur- 

 face of the porcelain. 



It has now been found that the difficulty 

 in seeing the adhering silica is not the chief 

 cause of loss when porcelain dishes are 

 used, but that a portion of the silica ad- 

 heres so tightly to the dish that it is not 

 possible to remove it by any ordinary 

 methods. In one case where 17.93 per 

 cent, of silica was obtained by using a 

 platinum dish, only 17.09 per cent, of silica 

 was obtained when a porcelain dish was 

 used. By suitable treatment with am- 

 monia, however, the silica adhering to the 

 porcelain dish was separated, and the total 

 silica, when using a porcelain dish, was 

 then found to be 17.97 per cent. Other 

 determinations of silica in porcelain were 

 reported, and although the variations from 

 the values obtained in platinum were not 

 so striking, the results were all low when 

 ordinary methods were employed for re- 

 moving the silica from the dish. 



An Occurrence of Native Sulphur in 

 Oconee County, Ga.: H. C. White. (By 

 title.) 



Report on the Water of Death Gulch, Yel- 

 lowstone National Park: G. B. Frank- 

 FORTER. (By title.) 



The Determination of Silica: N. Knight. 

 (By title.) 



On the Occurrence of Helium in Natural 

 Gas: H. P. Cadt and D. F. McFarlane. 

 (Read by E. H. S. Bailey.) 



physicaij chemistry. 

 Louis Kahlenberg, chairman. 



The Transition Temperature of Sodium 

 Bromide. A New Fixed Point in the 

 Thermometric Scale: T. W. Richards 

 and R. C. Wells. (Read by the chair- 

 man. ) 

 The results of this paper may be summed 



up in the following sentences: 



1. Pure sodic bromide is not to be ob- 

 tained by recrystallizing the ordinary com- 

 mercial samples, but must be made from 

 pure bromine and pure sodic carbonate. 



2. Prepared in this way, our salt upon 

 analysis was found to con-espond very 

 closely with the new atomic weight of 

 sodium, 23.008, if silver be taken as 107.93, 

 and bromine, 79.955, therefore, it was pre- 

 sumably pure. 



3. The less pure material on successive 

 recrystallization gave in every case a slight- 

 ly rising transition temperature as the 

 crystallization proceeded. Only the pur- 

 est material melted at a perfectly constant 

 point, therefore, constancy of melting 

 point is an indication of purity; but it is 

 safer to analyze the salt as well. 



4. When all precautions are taken it is 

 possible to duplicate the results for the 

 transition temperature with samples of salt 

 prepared in different ways and at different 

 times ^vithout great difficulty, a value 

 within .01 of the truth may be easily ob- 

 tained and further precautions make a 

 much greater accuracy possible. There- 

 fore, the point is one suitable to use in the 



