270 
MESSRS. W. R. HARTLEY ART) A. K. HURTIRGTOR OR THE ACTIOR 
Phenol, C,;H 5 .OH (Diagram No. 10).—Solutions in water containing the following 
quantities of the body were examined : y-jj-o, too> TTom T 2 V 05 tjjujTc i 2 8 00 ; 2 5 e 0 o* 
In this case, as in all the following, the intensity of all the absorption bands renders 
it necessary to reduce the dimensions of the ordinates to the curve, which represent 
the quantities of water used in dilution, otherwise the diagram would stretch to five 
times the length of those representing the hydrocarbons. The absorption of the rays 
more refrangible that 24 Cd was not extinguished by the dilution to tt§"oo> nor is if 
entirely destroyed by doubling such dilution. 
Thymol (Diagram No. 11).—This body is a methyl-iso-propyl-oxybenzene, 
rOH 
C f; H.J CH, 
L ch(ch 3 ), 
Solutions of the following strength were examined: 1 gramme was contained in 
100 c.c./ 1000 c.c., 2000 c.c., 5000 c.c., 7500 c.c., 10,000 c.c., 20,000 c.c., 40,000 c.c., 
80,000 c.c., 100,000 c.c. 
The smaller effect of dilution on the absorption rendered it necessary again to 
reduce the dimensions of the ordinates to half those of the phenol curves. 
It seems as if complexity of structure increases the intensity of the absorption bands. 
Pyrogallol, C 0 H 3 (OH) 3 (Diagram No. 12 ). — Solutions containing the following 
proportions of the substance were examined : T - 0 J ( jo> Worn Tooom 5 6000 .• TTOom 
and T7)T)W<7- After dilution has reduced the proportion of substance in solution 
t°.T oVo » rays beyond 18 Cd are faintly transmitted, with a proportion of yoo“o"o there 
is nearly complete transmission as far as 23 Cd, but there is still some absorption with 
1 
lOOOOO* 
Benzoic, hippuric, and phthalic acids being substances in which the carboxyl group 
occurs, are of much interest. 
Benzoic Acid, C 0 H-.COOH (Diagram No. 13). 
30005 50005 60005 8 0005 lOOOOs 1 50005 200005 400005 800005 
-Solutions containing* 
and 
120000 
2005 1 0005 
their weight 
O 
of substance were examined. 
The most diluted of these liquids still partially absorbed the rays beyond 23 Cd— 
that is to say, they were enfeebled. There is a feeble transmission of the rays between 
17 Cd and 18 Cd with a dilution of ^oVo* This extends to the main band of transmitted 
rays at y~ ( /j 0 , and a continuous spectrum is transmitted as far as 18 Cd with 
Phthalic Acid, C (; H t .(COOH) 0 (Diagram No. 14).—The general appearance of this 
and the preceding spectrum is remarkable, though there is a distinct difference between 
Solutions containing y^o, too m 
50005 60005 7 5 005 1 00005 1 50005 2 00005 400005 
them. 
i _l_ _ i_ _i _ _i__ i _i___ i 
600005 800005 1000005 1 200005 1 500005 2000005 2500005 3000005 
and 
400000 
ths. 
their weight were examined. The last solution on comparison with distilled water 
still showed a slight absorption of the extreme rays. It is the increased opacity of 
the latter substance which constituted the chief difference between the spectra of 
