402 



Browning — Influence of Acids 



recorded in Series II show that aqua regia has even less effect 

 as a solvent than nitric acid alone. In fact it seems to act 

 like hydrochloric acid alone, which practically has no solvent 

 effect, as shown by Dr. Mar's work previously cited. 









Series II. 

















Time be- 



Per ceDt 





BaS0 4 









tween pre 



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equivalent to 





Error in 





eipitation 



of 





Ba(XO,) 2 



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terms of 





and filtra- 



strong Total 





taken. 



found. 



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Averages 



tion. 



aqua regia. volum< 





grin. 



grm. 



grm. 



grm. 



hours. 



;3HC1: IHNO3). cm 3 



( 1) 



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i; 11 



In this connection I append the results of a few experiments 

 made to determine the effect of the presence of a considerable 

 amount of free nitric acid, on the precipitations of barium as 

 sulphate in cases where certain substances are present which 

 under ordinary conditions tend to hold up the precipitate. 

 Fresenius* has demonstrated this property in the case of 

 ammonium nitrate, Scheerer and Rube,t have shown that 



* Zeitschr. f. anal. Chem., ix, 62. f Erdm , Jour, prakt. Chem., lxxv, 113-116. 



