MESSRS. W. N. HARTLEY AND A. K. HUNTINGTON ON THE ACTION 
18 Cd and 23 Cd, with one part of the substance in 100,000 of water, and this band 
continues, though diminished in power, until 205,000 parts of water have been added. 
Absorption of the more refrangible rays beyond 26 Cd continue till 410,000 parts of 
water have been used in dilution. Had this diagram been drawn on the same scale as 
that representing benzene and the allied hydrocarbons, it would have extended beyond 
a length of 170 feet, each inch only of which would have represented a dilution with 
200 parts of water. 
The two following substances were examined on account of their close relationship 
to salicylic acid and its isomers :— 
Salicylate of Methyl, CgH^OH.COOCHg, BP. 
2 20°’7 
(Diagram No. 20 ).—This was 
rectified from about a kilogramme of oil of winter-green. Two sets of observations 
were made, and solutions containing the following proportions by weight of the sub- 
10 00> 1 5 (JO) ‘2 5 0 0* 5000* lOOOO) 15000) 3 
__A_ _l_ a11r l 
000 0) 4500 0) clliu 
60000' 
stances were used 
At first, all rays beyond 12 Cd are absorbed, and this condition continues until beyond 
when the rays between 17 Cd and 18 Cd are transmitted. The 
a dilution of 
1 5 00) 
absorption band lying between 12 Cd and 17 Cd becomes nearly extinguished by an 
addition of 45,000 parts of the diluent; but at the same time a second band of rays, 
lying between 25 Cd and 26 Cd, is transmitted, which gradually extends but does not 
overcome the absorption band lying between 1.8 Cd and 23 Cd until after a dilution 
with 60,000 parts of water. 
So. Heine. 
C 6 H n 0 5 
’ C g H,(OH)CH, 
following proportions of substance : ^q, 
The absorption band is highly characteristic. 
0 (Diagram No. 21 ).—Solutions examined contained the 
i 
8 0 U) 
and 
1600) 4000) 8000) 2 0000) 5 0 0 0 0' 
Transmitted rays, a little less refran¬ 
gible than 23 Cd, make their appearance in solutions containing 4^0 of substance, in 
addition to the continuous transmission of rays less refrangible than 17 Cd. In 
solutions containing woo 
the absorption band has practically disappeared. 
Ortho-intro-phenol, C 6 H 4 .N0 3 .0H, P 2 (Diagram No. 22 ).—Aqueous solutions only 
of the phenols were employed notwithstanding their very slight solubility in water. 
Solutions containing ^ 0 ! 
GO) 8000) 1 2000) 1 6000) 20000) 2 5000) 2 8000) 30000) 3 2000) 
1 — 1 — —Tooo, an d Foooo' °f their weight of the crystals 
3 5 0 00, 36000) 40000) 45000) 50000) 551 
were examined. 
Although this is a colourless substance it is remarkable how it cuts off nearly 
all but the visible rays, even when dissolved in 20,000 times its weight of water. 
When the dilution has reached 25,000, the rays a little beyond 11 Cd and 12 Cd are 
transmitted; at 35,000 a second band of rays lying between 18 Cd and 23 Cd makes 
its appearance ; and at 60,000 there is almost a continuous spectrum nearly as far 
as 26 Cd, though traces of an absorption band are seen even in presence of 120,000 
parts of water. 
Para-nitro-phenol, l - 4 (Diagram No. 23).—This substance is strongly coloured 
