MICROCHEMICAL REACTIONS OF THE COMMON ELEMENTS 299 



stated, no deleterious influence on the precipitation of the oxa- 

 lates of calcium and strontium, we meet, in the case of barium, 

 with a most interesting and remarkable reaction. Owing to the 

 formation of double oxalates of barium and iron or barium and 

 aluminum, instead of the typical fibrous bundles of needles 

 and crystallites, there are now obtained tufts and bunches of 

 very long exceedingly fine curving hair-like crystals (trichites) 

 of characteristic appearance. The chemical composition and 

 formulas of these compounds have not yet been definitely ascer- 

 tained. 



In order to obtain this interesting compound, proceed as 

 follows: To the test drop containing barium, add ferric chloride 

 in sufficient amount to impart a faint but distinctly yellow color; 

 then add a fragment or two of sodium or ammonium acetate; 

 stir. The yellow color should now have changed to a reddish 

 tint. Into this drop, thus prepared, cause a drop of oxalic acid 

 to flow. Tufts and sheaves of very fine hairs soon appear. The 

 hairs rapidly grow longer and longer and soon begin to curve in 

 a most peculiar manner. The presence of calcium or strontium, 

 or both, in even large amounts does not appear to have any 

 serious influence on the formation of this double oxalate of 

 barium and iron, save that its separation is often somewhat re- 

 tarded. In such mixtures the oxalates of calcium and strontium 

 first appear in their usual form, then after a time the hair-like 

 tufts of the double oxalate appear. If the quantity of barium 

 is quite small, in proportion to the iron, little rosettes of radiating 

 needles are obtained, separating near the edges of the drop. 



Aluminum gives rise to the formation of a similar product, 

 but the crystal masses are colorless, while those of the iron salt 

 are light brown. 



EXPERIMENTS. 



a. Test a salt of Ba with H 2 C 2 O 4 , in both hot and cold solutions. 



b. Make a mixture of Ca, Sr, Ba. Add H 2 C 2 O 4 . Repeat the experiment in 

 HN0 3 solution; after a few minutes, decant the clear solution, concentrate slightly 

 and add NaC 2 H 3 O 2 . 



c. Try the effect of the presence of FeCl 3 on the precipitation of oxalates of Ca, 

 Sr, Ba; first each element separately, then in mixtures of Ca and Ba; Sr and Ba; 

 Ca, Sr and Ba. 



