41 
1912-13.] The Absorption of Light by Inorganic Salts. 
solutions. It • may be seen that the absorption in the visible spectrum 
increases with dilution in the case of ferric nitrate and sulphate, but 
decreases with dilution in the bromide. With ferric chloride the absorption 
at first decreases with dilution and then slightly increases. This increase 
with dilution at low concentrations may probably be due to the formation 
of colloidal hydroxide. As seen from Table II., the absorption by the 
ferric chloride solution of concentration c = *01 increased greatly when the 
Table II. — Variation of A with c. 
Fe 2 Cl 6 .12H 2 0. 
Fe 2 Br 6 . 
Fe 2 (N0 3 ) e .18H 2 0. 
Fe 2 (S0 4 ) 3 . 
FeCl 2 . 
FeS0 4 
^7 
tu 1 
o 
Fresh. 
Old. 
Fresh. 
Old. 
Fresh. 
Old. 
Fresh. 
Old. 
c. 
c. 
•453/4 
1-0 
5*57 
4-63 
2-41 
1-81 
4-0 
•39 
1-5 
•074 
•7 
5-95 
4-87 
2-55 
2-72 
2-0 
T8 
•75 
•074 
•4 
6-48 
5*48 
3-37 
2-71 
1-0 
•16 
•5 
T2 
T 
14-6 
14-7 
63-4 
58-0 
10-49 
8-77 
5-61 
4-87 
•5 
•22 
hi 
14-9 
58-4 
22-6 
54-7 
13-15 
12-75 
12-4 
13-7 
•529 
2-0 
6*85 
4-73 
4-0 
•033 
1-5 
•032 
1-5 
3-53 
2-52 
20 
•051 
•75 
•048 
1-0 
1-72 
1-25 
1-28 
•85 
’•68 
•63 
1-0 
•077 
•7 
1-26 
1-02 
1-21 
•98 
•77 
•75 
•5 
•097 
•4 
1-26 
1-04 
353 
27-5 
1:35 
1-03 
•99 
•90 
• • • 
•1 
1-68 
1-62 
7-59 
5-90 
1-92 
1-73 
1-92 
1-95 
•01 
3-49 
17-5 
4-90 
9-88 
2*37 
3-84 
6-53 
5-90 
•653 
2-0 
•26 
•23 
4-0 
•057 
1*5 
TO 
1-5 
•22 
•21 
2-0 
•067 
•75 
•094 
1-0 
T7 
T8 
11-8 
8-01 
•14 
T3.| 
•18 
T4 
1-0 
•082 
•5 
T1 
•7 
•15 
2-52 
1-91 
•15 
•09? 
•20 
T5 
■5 
•12 
•4 
T3 
•66 
•56 
•16 
T6? 
•23 
•22 
• • • 
•1 
•37 
•33 
• • . 
•01 
4-2 
... 
solution had been standing for six weeks. The solution was then no longer 
clear even after being filtered through ordinary filter paper, but contained 
a great number of fine colloidal particles. After standing for a year the 
solutions of the ferric salts of concentrations c = T0, - 7, and ‘4 were found 
to be quite clear; the solutions of concentration c — m 1 contained fine 
colloidal particles, and those of concentration c = *01 contained large 
particles, which in the case of the nitrate and sulphate had deposited 
themselves at the bottom of the bottles in which they were kept, leaving 
the solutions practically colourless. 
