Mr. A. Gages on Vivianite. 183 



exception to what has just been stated, as it has been found in 

 the horns of the Irish elk, and even in human bones. 



Stalagmitic-like concretions and nodular masses of phosphates 

 appear to be immediately derived from organic bodies, and may 

 have been formed by the double decomposition of phosphate of 

 lime, held in solution in water, by carbonic acid and salts of 

 metallic oxides, or by the reverse action of soluble salts of me- 

 tallic oxides upon earthy phosphates. 



One of the most interesting mineral phosphates is the blue 

 protophosphate of iron, which, when crystallized, is called Vivian- 

 ite, — the earthy varieties being known as blue iron earth, Augla- 

 rite, &c. This phosphate is found either crystallized or amor- 

 phous in all formations, from the oldest to the most recent ; and 

 there is no doubt that it can be formed in a very brief space of 

 time, as the observations of Schlossberger show that the blue 

 matter sometimes found in the pus of ulcers has the composition 

 of Vivianite, the iron being derived from the disorganized blood- 

 corpuscles. 



Considerable doubt exists as to the true constitution of Vi- 

 vianite. Rammelsberg assigned to a specimen analysed by him 

 the formula 



4(3FeO,PO^)-l-2(3FeO,P05)-f-3Fe2 03, 2P05+1GHO, 

 or 



6(3FeO,POH8HO)-f3Fe2 03,2PO*4 8HO. 



The observations of Barreswil upon Abich's salt, 



3(FeO, S03) 2(Fe2 0^ 3 SO^) + 4H0, 



which he obtained of an indigo-blue colour, appears to lend sup- 

 port to the view that Vivianite contains sesquioxide of iron. On 

 treating the blue sulphate with phosphate of soda, he obtained 

 a blue salt which was not decomposed by water. Rammelsberg 

 assigned to this artificial phosphate the formula 



2(3 FeO, PO^) -f3Fe^ 0^, 2P05+ 16 HO. 



The ordinary basic phosphate of protoxide of iron, obtained 

 by adding a solution of basic phosphate of soda, 3NaO, PO^ 

 drop by drop, to a solution of a protoxide salt, and which has the 

 composition 3 FeO, PO^ is white when first thrown down, but 

 gradually becomes blue on the filter. If the blue colour be 

 owing to oxidation, it must take place very rapidly, and only a 

 very small portion of sesquioxide must be necessary to ])roducc 

 the blue colour ; for this is found to have penetrated the whole 

 mass on the filter, even before it is wholly washed. 



This is fiirtlur shown by dissolving a portion of the blue 

 earthy phosphate in weak hydrochloric acid, and adding sesqui- 



