342 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[October 28,187L 
present in only small amount, they do not interfere 
seriously with the production of chloral. 
Aldehyd .—This has already been mentioned as 
the source in foreign spirit of crotonic chloral. 
As concomitants of the chloral we have then 
already chloride of ethyl, crotonic chloral, acetic 
acid, ether (?), and the numerous compounds derived 
from the fousel oils. But this is not all. These 
substances are, most of them, susceptible in their 
turn of the substituting action of chlorine. Thus 
from chloride of ethyl may be formed the following 
series:— 
Monochlorinated 
Diclilorinated 
Trichlorinated 
Tetraclilorinated 
Pentaclilorinated 
Ethyl Chloride 
C 2 H 5 C1. 
c 2 h 4 ci 3 . 
c 2 h s cl. 
c 2 h 2 ci 4 . 
c,hci 5 . 
C 2 C1 6 . 
From ether a similar series results, and probably 
all the other compounds referred to as originating 
in the fousel oils, yield b}^ the same action at least 
one cliloro-substitution product. 
{To be continued.) 
THE 
ESTIMATION OF 
LIQUIDS. 
COLOUR IN 
BY BOVERTON REDWOOD, F.C.S. 
Secretary and Considting Chemist to the Petroleum 
Association. 
It occasionally happens that the estimation of the 
amount of colour in a liquid is an operation of con¬ 
siderable importance. The following remarks have 
special reference to a notable instance of this afforded 
in the case of refined petroleum, the commercial 
value of which is to a great extent dependent upon 
its colour; since, however, they are in the main ap¬ 
plicable to many other cases of a similar nature, not 
only in technical, but also in scientific chemistry, 
they may be considered to be of general interest. 
The colour of refined petroleum has usually been 
measured by comparison with samples kept as arbi¬ 
trary standards; such standard samples being in 
this country commonly contained in glass bottles of 
the ordinary form, and about 8 inches in height, 
while in America square bottles are preferred. The 
first difficulty in this mode of operating to which re¬ 
ference may be made, arises from the liability of the 
standard samples to change colour, and this is but 
imperfectly overcome by keeping the samples pro¬ 
tected from the action of light. The Americans have, 
however, provided a remedy, which consists in the 
use of stained glass bottles, which, when empty, are 
the same colour as “ white glass” bottles filled with 
the standards. This ingenious device is nevertheless 
no remedy for the next difficulty which lies in the 
fact that in cases of dispute, which not unfrequently 
occur between buyers and sellers, the system of com¬ 
paring in bottles is not found to be sufficiently deli¬ 
cate ; and opinions frequently differ as to whether a 
certain sample is equal to the standard or not, espe¬ 
cially when the samples are observed against a clear 
sky, the blue colour of the firmament forming a bad 
background. The obvious way out of this dilemma 
was to employ a larger body of liquid, and Letheby’s 
water-tubes, long test-tubes, or tall hydrometer- 
glasses held over a white plate or sheet of paper, 
have been used to contain the samples. The fluores¬ 
cence of the liquid, however, prevented this mode of 
procedure from being as applicable as in the case of 
potable waters, for instance; and although the fluo¬ 
rescent appearance may be got rid of by coating 
the sides of the vessels with some opaque material, 
the plan hardly answered better than that of com¬ 
paring the samples in bottles, until it occurred to 
Mr. R. P. Wilson (London), who with the writer 
was engaged in the determination of the colour of 
certain specimens of petroleum, to place a mirror 
beneath the tubes as a substitute for the white plate. 
It was at once evident that this constituted a great 
improvement, for instead of having to look down the 
two tubes alternately, it was merely necessary to 
glance at the mirror, where two well-defined discs 
of colour corresponding to the colour of the liquids 
appeared in juxtaposition convenient for compari¬ 
son. Mr. Wilson was, however, not content with 
this arrangement, which was still subject to the ob¬ 
jection attaching to the use of a liquid standard, but 
elaborated the idea until he produced the apparatus 
of which the following is a description, ancl which 
he has since patented. 
The invention, which Mr. Wilson terms a cliromo- 
meter, consists of two tubes of equal length (those 
used in the examination of petroleum being prefer¬ 
ably of glass 10 inches long by i inch internal dia¬ 
meter, and encased in brass tubing), marked a a in 
figs. 1 and 2, attached side by side to the hinged lid 
of the box which encloses them when the apparatus 
Fig. 1. 
