Chap. IV. ] 
PSILOMELANE. 
103 
not so much ferric manganate available to be converted into ferrous 
and manganous manganates and oxygen. Still the difference, namely 
4'47 of ferric manganate, only corresponds to an oxygen error of 0"38. 
In the case of the excess of 1"52 of oxygen, this excess can be used to 
convert manganous manganate into manganic manganate according to 
the following equation : — 
7Mn2Mn05 + 10 0=3JIn4(Mn05)3 ; 
according to tliis equation 152 of oxygen converts 16"29 of Mn2Mn05 
into 17-81 of Mn4(Mn05)3. 
In analyses 1157 and A. 381 the surplus oxygen is enough to convert 
8'57 and 13-29 of MnaMnOg into 9 37 and 14-51 of Mn4(Mn05)3, re- 
spectively. Making these alterations, the five analyses can be rewritten 
as follows, leaving the two in which there is an oxygen deficit unaltered 
and omitting all the constituents that do not come into the manganate 
molecules : — 
r 
Guguldoho. 
Avagudem. 
Tekrasai. 
Tekrasai. 
1 Tekrasai. 
1157 
A. 372 
A. 380 
A. 381 
J. 917 
Fe4(Mn05)3 . 
2-95 
11-22 
0-41 
0-14 
0-98 
AU(Mn05)3 . 
0-38 
8-92 
0-75 
1-88 
113 
Mn4(Mn05)3 . 
9-37 
14 53 
17-81 
Ba2Mn05 
0-04 
3-25 
20- 14 
6-89 
2-76 
Ca2Mn05 
0-40 
1-04 
0-15 
0-56 
0-90 
Mg2Mn05 
0-41 
0-57 
0-57 
O-oO 
0-36 
K4Mn05 
4-79 
502 
0-31 
3-60 
4-07 
Na4Mii05 
0-82 
0-04 
0-27 
0-33 
0-33 
Co2Mn05 
017 
0-25 
0-42 
0-34 
0-59 
Ni2Mn05 
0-34 
0-25 
0-08 
Cu2]VIn05 
007 
0-13 
0-07 
0-02 
Zn2Mn05 
0-24 
0-49 
0-65 
0-90 
H4Mn05 
1312 
14-66 
12-73 
10-03 
10-22 
]VIn2Mn05 
6fvI7 
52-90 
62-28 
59-10 
58-8S 
98-62 
98-18 
98-99 
98-87 
98-9? 
If now we want to find out the molecular ratio of manganates of the gene- 
ral formula R^qMuOs {i.e. all the manganates above, except the ferric, 
manganic, and aluminic manganates), to the manganates of the general 
formula R"' 4(Mn05)3 {i.e., the ferric, manganic, and aluminic manganates), 
then the simplest way is to take the simi of the quantities of the group 
