Intelligence and Miscellaneous Articles. 77 



ON THE FERRIC AND FERRI-MANGANI-TUNGSTIC ACIDS. 

 BY M. A. LAURENT. 

 When a mixture of nitre and carbonate of potash is fused with 

 excess of wolfram, a product is obtained which is partially soluble 

 in boiling water, and deposits on cooling a brown gummy salt. 

 This salt, treated with hydrochloric acid, yields, when the solutionis 

 evaporated with heat, large prisms with six regular faces, the com- 

 position of which may be referred to a new type, which will be 

 W^ O'^ W. 



This new tungstate exhibits a very singular combination and pro- 

 perties. It contains peroxide of iron, potash, tungstic acid and 

 water, either W^ O's K* f^ H^+ 6Aq, or W' O'^ K« f^ H*+ 7Aq. 



Concentrated acids do not precijjitate tungstic acid from it, and 

 the alkalies do not separate peroxide of iron ; ferrocyanide of potash 

 does not occasion any colour. Lastly, what is most surprising is, 

 that sulphuretted hydrogen does not reduce the peroxide to prot- 

 oxide of iron ; the same is the case with sulphuret of ammonium. 

 But when the solution of this salt is heated with potash or ammonia, 

 pertungstate of iron is gradually precipitated, and acids occasion an 

 abundant precipitate of tungstic acid. 



When heated to 392° F. it loses 7 atoms of water, and then redis- 

 solves immediately in water. Heated to dull redness, it loses only 

 two-thousandths of water, and becomes insoluble. Guided by the ideas 

 which he has stated with respect to the constitution of these salts, 

 the author thought that the latter ought to retain two- or three- 

 thousandths of water at a red heat ; to satisfy himself on this sub- 

 ject, he heated in a narrow tube a mixture of litharge and of the 

 calcined salt. A slight moisture was deposited, the weight of which 

 was two-thousandths. Thus we have a salt which retains, at near 

 a dull red heat, four-thousandths of water, and this small quantity is 

 sufficient to impart peculiar properties to it, which it totally loses on 

 being deprived of it. It corresponds to the H^ indicated in the 

 formula. 



In thus arriving, by theory, at results which come within the limits 

 of errors of observation, the author states that he cannot give them 

 with too much reserve ; for under similar circumstances, it is to be 

 feared, that in spite of himself, the observer is influenced by precon- 

 ceived ideas. 



Tills ferritungstate, treated with bichloride of platina and alcohol, 

 gives, after the separation of the chloroplatinate of potash and evapo- 

 ration to the consistence of a syrup, crystals of ferritungstic acid ; 

 with barj'tes and potash, two salts are obtained which contain 

 Ferritungstate of potash, W* 0'« f* K* H*-f 7Aq. 

 Ferritungstate of barytes, W^ 0"'f^Ba'^''-|-3Aq. 

 The ferritungstate of ammonia, calcined at a red heat and then 

 treated with ammonia, yields a solution which contains iron ; but 

 the greater part of the ferritungstic acid is converted mto common 

 tungstic acid. 



When, after having treated wolfram with aqua regia, and washed 

 the residue imperfectly, it is treated with ammonia, a solution is ob- 



