Scheerer on Isomorphism. 191 
agreeing with Vogel’s analysis of the Bodenmais vivianite. The 
chemical difference between both minerals would consist there- 
fore merely herein, that in the former a smaller quantity of the 
protoxyd of iron is replaced by water than in the latter. 
5. Vivianite from the Mauritius. 
According to the analysis of Laugier it consists of phosphoric 
acid 21, protoxyd of iron 45, water 34= 100. 
From these numbers we can, it is true, surmise no great accu- 
racy, nevertheless they afford an oxygen ratio of 11-:77P: 
10:25 Fe : 30: 115, corresponding approximately to the for- 
mula Fe* P+ 15H, according to which the oxygen ratio should 
be 10: 10 : 30, In this mineral, therefore, the whole of the 
water appears to exist as a hydrate, The formula however ad- 
mits of being thus men (Fe) if P, in which case the whole 
of the water figures as bas 
B. Phosphates of Copper. 
As oxyd of copper is not isomorphous with magnesia, protoxyd 
of iron, &c., it of course cannot be assumed that three atoms of 
water replace one atom of oxyd of copper. From grounds which 
I will afterwards explain, there is more than a probability that 
two atoms of water can replace one of oxyd of copper. at 
less water should be required to replace one atom of oxyd of cop- 
r than one atom of magnesia, is sufficiently substantiated by 
the different basic qualities of these compounds. In calculating 
the oxygen ratio of the following phosphates and arseniates of 
copper, it is assumed, as yet hypothetically, that 2H =1Cu. 
“1. Libethenite. 
The crystallized Libethenite consists, according to Berthier’s 
analysis, of phosphoric acid 28:7, oxyd of copper 63:9, water 
‘A=100°0, This gives, upon the above supposition, an oxygen 
ratio of 16-08P : 16-18(Cu), corresponding exactly to the formula 
(Cu) P, which is the formula ef the Comwall vivianite and of 
the eathy vivianite from Hillentrup. 
2. Phosphorochaleite. 
Rammelsberg calculated from Lynn’s dpalysis of the phos- 
phorochalcite from Rheinbreitenbach, the formula Cu‘ P+5H, 
tie completely with the formula here adduced for the 
phosphates. According to the analysis perhaps a portion ! 
for a certainty but a — ‘one) of the oxyd of copper may 
7% 
