34 J. W. Mallet on the Norwich Phosphate. 
The iron and manganese appeared to exist altogether as ses- 
quioxyds. The lithia contained a little soda, but the quantity of 
the latter was too small to separate and weigh. 
The mean of these results makes the composition of the 
mineral— 
. Atoms. 
Phosphoric acid, - - - 43:04  -598 
Peroxyd of iron, = - - - 29°50 meee 654. 
Sesquioxyd of manganese, - 22°59 285 
Lime - ares - - 09 003 
Magnesia, aes - ae ‘73 036 > *163 
Lithia, - ee. - - To 124 
Water, - - - - - 2°05 228 
99°79 
Hence we have the complex and not very probable formula 
s846s+R5hs47H; but if we consider, as suggested by Mr. 
that the iron and manganese originally existed as protoxyds, 
the above numbers give the equivalents of phosphoric acid, pro- 
toxyds, (adding in the lithia and earths), and water, in the ratio 
598 : 1471: 228, or very nearly 2:5:1, although the water does 
not amount to quite 1 atom. Hence we have the much simpler 
formula, R5f2+H, which is that of Damour’s alluaudite, if we 
reduce the per- to protoxyds as above, though that mineral differs 
from the present in containing soda instead of lithia, and in the 
manganese actually existing toa great extent as protoxyd, while 
in the substance from Norwich the peroxydation of the metals has 
been completed. - 
There have been already described three phosphates occurring 
in nature which have this general formula, with the exception of 
the water, which varies in amount in each—Ist, this mineral from 
Norwich and the Alluandite from Limoges, the formula of which 
is RsP2+H; 2nd, Heterosite or Hetepozite, of Dufrénoy, from Li- 
moges, with the formula &5~2+2H; and 3rd, Hureaulite, also from 
Limoges, “and represented by Rsf2+sH. Whether any of these 
minerals deserve to rank as distinct species seems very doubtful. 
It would seem more likely that they are all the mere products of 
a gradual alteration, in the course of which “the heavy metals 
were more or less peroxydized, water was taken up, and probably 
some of the alkaline constituents of the mineral were lost. - 
This last mentioned action seems indicated as having affected 
the lithia of the phosphate from Norwich, since the phosphoric 
acid found is a little in excess of that required by the formula. 
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