ABSTRACTS 



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 this issue. 



CHEMISTRY. — Some qualitative tests for gum arabic and its quantita- 

 tive determination. C. E. Waters and J. B. Tuttle. Bureau 

 of Standards Technologic Paper No. 67. Pp. 15. 1916. 



A study of many of the published tests for the gum, as well as a 

 search for others than the few that proved to be reliable. It was found 

 that basic lead acetate gives the most characteristic reaction, while 

 mixtures of copper sulphate and sodium hydroxide, and of neutral 

 ferric chloride and alcohol are of value as confirmatory tests. Dex- 

 trin and gum ghatti were subjected to the same tests. 



A summary of the more important methods that have been proposed 

 for the quantitative estimation of gum arabic is next given, followed 

 by a description of the steps that led the authors to the use of alcoholic 

 copper acetate-ammonia solution for this determination. C. E. W. 



CHEMISTRY. — The determination of barium carbonate and barium 

 sulphate in vulcanized rubber goods. John B. Tuttle. Bureau 

 of Standards Technologic Paper No. 64. Pp. 5. 1916. 



Specifications for purchasing rubber goods frequently permit the 

 use of barytes (barium sulphate) as a mineral filler without having the 

 sulphur which if contains count as part of the specified total sulphur. 

 In such cases the barium sulphate must be determined in order to 

 properly correct the total sulphur. 



When barium sulphate only is used, the amount present is readily 

 ascertained by determining the total amount of barium present. If 

 barium carbonate is used, it is necessary to separate the two salts. 

 By means of tests made on compounds of known composition pre- 

 pared at the Bureau of Standards, a method has been devised which 

 permits the quantitative determination of barium carbonate in the 



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