930 
FACTS AND OBSERVATIONS. 
The Effect of Artificial Light on the Eyes. — 
The Chemical News takes the following interesting paper from 
Les Mondes. It is by M. V. Meunier. The author states 
that the great difference between sun and artificial light is 
due to the fact that, of the light emitted from the former, 
about half the quantity of rays are luminous and calorific at 
the same time; but, as regards our artificial light, for ordi- 
nary oil (colza oil), the amount of non-luminous, yet calorific, 
rays is 90 per cent. ; for white-hot platinum, 98 per cent. ; 
alcohol flame, 99 per cent. ; electric light, 80, and gas light, 
90 per cent. ; while for petroleum and paraffin oils, the 
amount is 94 per cent. It is this large quantity of caloric 
rays in artificial light which causes the fatigue to the eyes ; 
but this inconvenience may, according to the author, be 
almost entirely obviated by intercepting the thermic rays by 
glass, or, better yet, mica plates. The use of these renders 
the light soft and agreeable to the eyes. 
Further Researches on Cotton Respirators. — 
Dr. Jouglet has been experimenting on the use of cotton 
respirators, and states that, by their application, the disease 
known as miner’s anaemia, and also the dangers of the effects 
of lead, copper, and mercury, to those who have to handle 
these metals, or work in vapours or dust thereof, may be pre- 
vented . — Comptes-rendus. 
New Purifying Agent. — M. Marixhas taken, in France, 
a patent for the application of fluosilicic acid for the purifying 
of beetroot and other saccharine juices. The saccharine 
juices are first diluted with a sufficient quantity of water, to 
take away the viscosity of these fluids, sufficient fluosilicic 
acid is then added to precipitate all the potassium salts pre- 
sent; and next, chalk is added to saturate any excess of the 
acid. The fluid is then filtered, in order to obtain a clear 
liquid, and this is afterwards treated in the usual manner. — 
Journal of the Society of Arts . 
Iodine. — Professor Wagner, in his reports, says that the 
manufacture of iodine from Chili saltpetre already amounts 
to 30,000lb. per annum. The method invented by Thiercelin 
for its reclamation from the crude material is as follows : — 
The mother liquors resulting from the manufacture of salt- 
petre are treated with a mixture of sulphurous acid and sul- 
phite of soda, in proper proportion, and the iodine will be 
precipitated as a black powder. The precipitated iodine is 
put into earthen jars, on the bottom of which are layers of 
quartz sand, fine at the top and coarse at the bottom ; from 
