TRANSACTIONS OF THE SECTIONS. 67 
Sulphurous acid, when moist, acts powerfully as an acid on vegetable colours, 
and bleaches the more fragile among them. If thoroughly dried, it may be 
kept for months in contact with dry colours without altering them. Under the 
influence of sunlight, however, it recovers to some extent its bleaching power, so 
far as the wallflower tints and the litmus are concerned; but on the yellow rhubarb 
paper it has acted like an alkali, and changed it slightly to a brown. 
Sulphuretted Hydrogen acts as a weak acid, and readily as a bleacher when moist, 
but becomes inactive in both respects if made dry and kept in darkness. With the © 
assistance of sunlight, it recovers in no inconsiderable degree its bleaching power, 
especially over litmus, and like sulphurous acid, it changes the yellow rhubarb paper, 
like an alkali, to a brown. 
Oxygen is a well-known bleacher when moist, and especially when nascent, but 
when dry, its action on colouring matter in the dark is extremely slow. In sunlight, 
however, it recovers its bleaching power, especially upon litmus. : 
Carbonic Acid, when moist, acts as a weak acid ; when dry, it loses all action upon 
colouring matter, but with the assistance of sunlight, it acquires a slight power of 
bleaching. 
Nitrogen has no appreciable action, whether moist or dry, upon colours ; but a faint 
bleaching action is exerted by it under exposure to sunlight. 
Hydrogen is without any action, when dry, upon colours, and is the least increased 
by the influence of sunlight in bleaching action, but does acquire a slight decolorizing 
power when exposed to sunlight. 
A mixture of Carbonic and Sulphurous Acid acts like sulphurous acid alone. 
The general result of this inquiry, so far as it has yet proceeded, is, that the 
bleaching gases, viz. chlorine, sulphurous acid, sulphuretted hydrogen and oxygen, 
lose nearly all their bleaching power, if dry and in darkness, but all recover it, and 
chlorine in the most marked degree, by exposure to sunlight. 
The second result, which must however be considered less certain than the first, is, 
that the southern tubes, which were exposed directly, exhibit bleaching action more 
decidedly than those hung within a room where the light had to pass twice through 
glass before reaching the colour, 
Whether the bleaching observed in the case of nitrogen and hydrogen was owing 
to any chemical action of those bodies, or was only such as might have occurred ina 
vacuum, I cannot determine, The experiments I have described can be considered 
nothing more than the commencement of what cannot but prove a protracted inquiry, 
which ought further to include the remarkable substance ozone, which ranks next to 
chlorine as a bleacher. 
On the presence of Fluorine in Blood and Milk. 
By Grorce Witson, M.D., F.R.S.E. 
The author having resumed the examination of this subject in the present summer, 
on a larger scale, and by simpler processes than he had employed for his communi- 
eation to the Royal Society of Edinburgh in 1846, has presented the following sum- 
mary of his results. i 
In my former examination of blood, I obtained a good result only when the serum 
alone was employed. This summer however I have employed the fresh-drawn 
blood of the Ox. About twenty-six imperial pints or three gallons of blood were made 
use of. This was obtained from different animals in quantities of about nine pints at 
a time, as this was as much as could be conveniently evaporated at once. The re- 
duction of the blood to ashes was a tedious and not very pleasant process, but with 
the help of a powerful furnace and the active cooperation of my assistant, Mr. Ste- 
venson Macadam, who took great pains with the whole process, I succeeded in the 
course of a month in reducing the whole quantity to well-burned ashes. These ashes 
contained some unburned charcoal, but not in large quantity, and presented the 
ta of two distinct substances; the one a dark red mass, owing its colour to 
the peroxide of iron; the other a white fused salt, having a strong pure saline taste, 
_ and consisting in greater part of chloride of sodium. ‘The presence of this substance 
interfered with the detection of fluorine, by evolving a large volume of hydrochloric 
acid, when the ashes were treated with oil of vitriol, which carried away any hy- 
drofluoric acid evolved simultaneously. It was necessary accordingly to remove the 
: j F2 
