abstracts: analytical chemistry 599 



INORGANIC CHEMISTRY.— r/z^ thermal dissociation of sulfur di- 

 oxide. J. B. Ferguson. Journ. Amer. Chem. Soc. 41: 69-72. 

 January, 19 19. 



The degree of dissociation and the equilibrium constants for the 

 dissociation of sulfur dioxide have been calculated from the equilibrium 

 measurements of the reduction of sulfur dioxide by carbon monoxide 

 and the dissociation of carbon dioxide, and the results of these calcu- 

 lations for a number of temperatures and pressures are given in this 

 paper. The values obtained confirm the experimental results which 

 indicated that the dissociation was too slight to be directly studied by 

 the present available methods. J. B. F. 



ANALYTICAL CHEMISTRY.— A contribution to the methods of glass 

 analysis, with special reference to boric acid and the two oxides of 

 arsenic. E- T. AllEn and E. G. ZiES. (Geophysical Lab. Papers 

 on Optical Glass, No. 5.) Journ. Amer. Ceramic Soc. i: 739- 

 786. Nov., 1918. 



Arsenic. An accurate method for the separation and determination 

 of both trivalent and pentavalent arsenic in glasses is described. The 

 separation depends on the volatilization of the trivalent arsenic as 

 AsFa when the glass is heated with hydrofluoric and sulfuric acids, 

 while the pentavalent arsenic remains in the residue. The procedures 

 described for arsenic in glasses are generally applicable to substances 

 in which the arsenic can be transformed into sulfide without loss, and 

 are highly accurate. A comparison of the iodometric method and the 

 magnesium pyroarsenate method for arsenic in glasses is made. The 

 former has the advantage in accuracy, and also in speed except where 

 occasional determinations are called for. 



Boric Acid. For the determination of boric acid we have found 

 that Chapin's method is very reliable and yields highly accurate re- 

 sults. It has been shown that in order to obtain very acciurate results 

 a "blank" must be made and the value applied as a correction to the 

 amount of boric acid found. The correction is small and for ordinary 

 work can be neglected. The accuracy of the method is very appre- 

 ciably affected by relatively large amounts of arsenious acid but not by 

 arsenic acid. Relatively large amounts of fluorides appreciably affect 

 the accuracy of the determination but do not seriously impair its use- 

 fulness for ordinary work. 



Other Determinations. Experience with the following cases in glass 



