GLEANINGS 
SCIENCE. 
No. 6 . — June, 1829 . 
I . — On Colouring Matter, 
Circumstances having occasioned roe to be engaged in the preparation of dyes, 
my attention was naturally turned towards the investigation of their properties ; and 
as during my researches the result of many experiments was decidedly opposed to 
the notions which at present obtain in chemistry, a system entirely new was neces- 
sarily forced upou me. As facts could not be reconciled with theory, it was quite 
clear that the theory could not be just : it therefore became necessary to compare 
facts and theory together; to discover the cause of tlieir disagreement ; to make the 
theory conform" to facts ; and to endeavour to find out a number of laws, constant and 
uniform in their operation, w hich should constitute the science of those arts which 
colours have created. The observation and experience of any one individual will 
always be exceedingly limited ; and the inferences which he may draw from thein 
will often be erroneous : as therefore I profess to have no interest apart from that ot 
truth, so I have no wish that anv opinion of mine, resting only on my own unsup- 
ported experiments, should have any other influence than that ot exciting inquiry. 
Icould havewished preparatory to the enunciation ot ray own views, to examine some 
of the facts respecting colouring matter* recorded by Doctor Bancroft, in his Philo- 
sophy of Colours, as also his opinions on them ; but as this would occupy too much 
space for my present purpose, I shall proceed to submit a few.gcneral principles, 
after which I shall adduce some of the chief facts upon which they are founded. 
1st. Oxygen is the principle of colour in colouring matter, and might therefore 
he as appropriately called chromogcn as oxygen. . ... 
2nd. Oxygen, in proportion as ite combines with colouring matter, increases thef 
depth of its colour, and diminishes its solubility. , , 
3rd. The WHOLE THEORY or DYING, ns regards colouring mutter, (excluding com- 
pound colours which will also be affected by it,) rests on considerations connected 
with the proportion of OXYGEN, as a constituent of the colouring matter, and upon 
proper views of chemical affinity. . . „ . . 
4tb. Oxygen, by entering largely into the composition of colouring matter, occa- 
sions a permanent and irrecoverable deterioration of its quality. 
5th. Alkalis are oxygenating agents 1 re j at i ve ly to colouring matter. 
6tk. Acids are dhsoxygenatiiig agents J 
7th. Many substances as they acquire oxygen have (whilst they continue below 
the point of saturation) tlieir disoxygenating power increased. 
3th. It cannot be calculated that two agents capable separately of attracting 
oxygen, from a third substance, will, if employed together, exercise their joint forces 
m the disoxygenation of this thi rd substance ; it is probable that they may act upon, 
and so counte ract each other ; and this is especially likely to happen where metallic 
a cids are concerned. . , _ „ 
9th. The atmosphere under one set of circumstances oxygenates ; under another, 
disoxygenates, relatively to colouring matter. There are some other points con- 
nected with chemical affinity and the fixity or fugitiveness of colours, but as they 
would carry me too far, I suppress them. 
* 1 have confined myself throughout this paper to speculations on colouring 
t lVerhaps ought to have added “ or changes one colour of a light shade toano- 
ther of a darker shade.” 
