538 G. Torossian — Reduction Test for Tungstic Acid. 



Procedure. 

 (a) Kubbing the finely powdered sub- 

 stance with aa iron spatula and 

 moistening the adherent coating 

 with concentrated hydrochloric 

 acid. 



Results, 

 (a) Blue color: developed in absence 

 of oxidizers and higher oxides 

 (e. g. ferric oxide), and without 

 interference by as much as 50$ 

 of molybdic acid. 



(6) Placing the powdered substance 

 upon aluminium (plate or foil) ; 

 moistening with a drop or two of 

 water ; addition of a drop or 

 two of concentrated hydrochloric 

 acid. 



(b) Blue color : developed in pres- 

 ence of oxidizers, ferric oxide, etc. 



(c) Placing the powdered substance 

 on aluminium (plate or foil) and 

 touching with a drop or two of 

 concentrated hydrochloric acid. 



(c) Wine-red color with superposed 

 layer of blue : developed, in ab- 

 sence of oxidizers, in tests applied 

 to tungstates of calcium, stron- 

 tium, barium, lead, zinc, and 

 rare earths (precipitated sodium 

 tungstate from a solution of rare 

 earth sulphates containing about 

 26% Ce0 2 ). 



(d) Placing of water (big drops) in a 

 single globule (not spread) upon 

 sheet aluminium ; sprinkling the 

 powdered substance upon the 

 globule ; addition of a very small 

 drop of hydrochloric acid to the 

 globule. 



(d) Blue color : developed in pres- 

 ence of insoluble carbonaceous 

 material, copper oxide, hematite, 

 lead oxides, sulphur, rare earth 

 oxides, or calcium fluoride. 



All the above tests, which are very simple, easily made and 

 rapid, give positive results under different conditions ; but the 

 delicacy of the test must necessarily vary with the composition 

 of the substance under test. It was found, for example, 

 that tungstic acid in mixture (fused) with sodium carbonate in 

 the proportion of 1 : 1000 (0*01 gram. : 10 grm.) was plainly indi- 

 cated by (<?), while the ordinary mode of testing with zinc and 

 hydrochloric acid failed to show any blue coloration ; that 

 while tests applied in the ordinary way (zinc and hydrochloric 

 acid, or stannous chloride) to a mixture of sodium tungstate 

 with sodium nitrate in the proportion of 1 : 50 failed to show 

 the presence of tungstic acid, as did also (a) and (c), the proce- 

 dures of (b) and (d) gave distinct and good reactions. 



The most generally applicable forms of these tests are plainly 

 the second (b) and fourth (d), the essential point of each being 

 the action of a very small amount of dilute hydrochloric acid 

 upon the powdered substance in contact with metallic 

 aluminium. 



Cleveland, Ohio. 



