sia 
Scheerer on Isomorphism. 205 
all, or does so only to a small extent; - the latter may 
often obtain with regard to some of the salts quoted towards the 
end of the above group. We have for instance, in the case of 
salt No. 9, the oxygen ratio 26°33 : 16-29 ; 19°30, whereas it 
ought to be 26°33 : 17: 56; 17-56. Possibly, therefore, in this 
compound 1-27 Mg (that i is to say 17:56-+16:29), are replacaeby 
1:74.34 (namely 19-30-17: 56), which would be exactly in the 
ratio required. On enquiring how it is that in fourfold hydrated 
three-fourths-carbonate of magnesia, no magnesia, or at least very 
little, is replaced by basie water, the twe following circumstances 
er themselves in reply. 1. The ten salts that we have men- 
cone were one and all, obtained at a boiling heat. 2. It must 
evidently be more difficult (from the reasons which I have entered 
into in the preceding paper relative to the kindred circumstances 
applicable to aspasiolite and serpentine) for water to find its way 
into a three-fourths-carbonate than into a semu-carbonate and ex- 
pel from thence a portion of the magnesia. 
addition to the hydrous magnesian ei. ag mention- 
ed, amounting in all to seventeen, which may be ranged in the 
two groups above deseribed, there are other five that have been 
analyzed, one of which however may be omitted here inasmuch 
as prior to its being analyzed (by. Dalton), it was dried at a temper- 
ature of 100°C. ‘The remaining four arg oa follows : 
ipa 
1. Five-fold hydrous simple carbonate "ey 
of magnesia, according to Fritsche, o) ot 29 ected 50 91 
2. Magnesia alba, according to Berg- pg ag. 30): 
mann 
3 po. do. according to Berzelius, 30°25 36:40 33°35 
A do. according to Fourcroy, 48° AQ: 12° 
The corresponding proportions of oxygen are— 
1. 18-466; 9-18Mg: 45312 
4:89 ; 15:48 : 10°68, 
4.3 
sal while the formulas resulting therefrom are— 
1 Qllg): 6-+2Hr. 3. Mgt C*+8H. 
: 2. (Mg)? C-+3, or (Mg)°C. 4. 3(Mg)C+ 
rie existence of the se s ae: fourth of these salts must, 
until established by more sea experiments, remain a matter 
of uncertainty. The two compounds alone, the composition of 
which is ascertained with sufficient precision, are, (Mg)? C+2H, 
Mg‘ C218, the oxygen ratio whereof was, | . 
Seconp Seriss, Vol. VI, No. 17.—Sept., 1848. 27 
ey 
;% 
