196 Scheerer on Isomorphism. 
contains also minute quantities of solid bases isomorphous there- 
with, as Fe, Mg, é&e. 
8. Alum. 
The alum formula, R S+Al S3 +24 H, is convertible to 
-8(R)? SAILS. 
9. Alum Stone, or Alumite. 
a Rammelsberg, from Cordier’s analysis of the crystallized alum- 
ite from Tolfa, attributes to this mineral the formula, ( KS+AlS°) 
4+3.l x, which involves, as it seems to me, an improbability, 
inastnuch as one portion of alumina and sulphuric acid are there d 
mbined as a neutral salt, while three times this quantity of 
alunite: in the form of a hydrate is noways combined with the 
acid at all. Changing the expression of the formula to (R)? S+ 
Al? S?, we get rid of the above improbable rai 
It cannot but be noticed that in the a ign 2 9 forthe 
different (neutral) sulphates, 1 atom is always introduced as 
water of i omg while six atoms #=2 ( R), acting the part 
bined with the sulphuric acid. This coincides 
very well with: ‘Graham’ s well known observation, to the effect 
that these salts by exposure to heat, yield up six equivalents of t 
water with far greater readiness than they do the seventh equiv- . 
alent, which is not expelled until the temperature is still farther : 
raised. Graham termed this last “ basic water,” and the former is 
water of crystallization. meen to my view of the matter, 
this nomenclature would be inverted.* 
At the close of these pisrticaiter to set about enumerating the a 
numerous facts in favor of the notion that water in the mine : 
kingdom, acts extensively the part of a base, seems to me a use- 
* Whether in fact in all the sulphates in question the quantities of the 1:1 atomi¢ 
bases (Mg, Fe, Mn, Co, Ni, Zn, Cu) are always in definite atomic proportion 
to the amount of basic water [as R : 2(8)], a circums i 
tance which, as we have 
seen, does not appear to obtain in other minerals (silicates, phosphates. and sili 
not aes iscrepancies observable i 
ists in their analysis o several of these sul hates, it be 
ratio between t :1 atomic base ed the Besi sata ae on le or ; 
: ught thong in ! 
way or another is to be sought for * akg vie Senin bs, per ane- 
ries of experiments directed to the formation of f erpatalltoed oot sulphates in chick. 
and (H) do not preety the definite proportion indicated above. But that such 
sulphates, if indee ey can exist, are fi <8 
stances, is of itself evi dest » are formed only under certain peculiar circum 
