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REPORT OF THE MICROSCOPIST. 623 
_ The above is a scientific statement of this phenomenon, but it can 
not convey to the general reader a definite idea of what is meant by 
fluorescence as applied to the fixed fats and oils. The following will, 
I trust, explain this remarkable behavior:of some special fixed fats 
and oils under certain conditions of treatment: 
Tf 100 grains of pure lard is triturated with about 400 grains of pure sulphuric 
acid freshiy prepared of a given specific gravity, 1.705, and poured immediately 
into a test tube, two-thirds of the free sulphuric acid falls to the bottom of the tube 
colorless, while the lard, changes quickly to a cinnamon color, and floats on top. Any 
of the fixed fats or oils in the list given below, treated in like manner, will color the 
acid in the lower two-thirds of the tube a yellow or port-wine color, as the case may 
be, perceived on holding the test-tube toward the light. If viewed after the lapse 
of twenty-four hours by reflected light and slightly in the shade the phenomenon 
of fluorescence is apparent in a greenish tinge of varying depths of color. 
FIXED FATS AND OILS, FLUORESCENT. 
I have tested the following fixed fats and oils, and find that they 
have the property of fluorescence in a marked degree: 
Palm. Polar Bear. Whale. 
Chaulnugra. Panther. Loon. 
Oleic acid, C. P. Otter. Alligator. 
Tallow Tree of China. - Raccoon. Pelican. 
Turkey Buzzard. Skunk. Opossum. 
Black-snake. Dog. Mullet. 
Horse. Domestic Turkey. 
I have also tested all the fats and oils employed in the manufacture 
of butter substitutes and find that none of them are fluorescent. 
Therefore, were any of the fluorescent fats or oils mixed with butter 
substitutes they would be detected by reason of this property. 
I have made a compound of lard and horse fat containing only 4 
per cent. of the latter, and detected the horse fat in the compound 
by its green fluorescence. 
To obtain these results successfully it is absolutely necessary to 
adhere strictly to a certain specific gravity of C. P., sulphuric acid, 
as laid down in my method. 
FATTY ACIDS; FIXED FATS, AND OILS NOT FLUORESCENT. 
Stearic acid, C. P. Beef fat, fresh. Castor oil. 
Stearine, C. P. Lard. Thibet Bear. 
Palmitic acid, C. P. Cotton-seed oil. Cat (wild and domestic). 
- Palmitin, C. P. Olive oil. Beef dripping. 
Commercial stearine. Benne oil. 
The fats and fatty acids in the above list marked C. P. are as 
nearly pure as can be made. 
DESCRIPTION OF THE PLATES, 
* 
PLATE 1. Butter crystals of the Jersey milch cow. 
PLATE 2. Butter crystals of the Shorthorn milch cow. 
PLATE 3. Butter crystals of the Holstein milch cow. 
PLATE 4. Implements used in the sulphuric acid color test. 
PLATE 7. Showing the color reactions with suiphuric acid of pure lard, cotton seed 
oil, and compounds of lard, cotton-seed oil and stearin (fictitious lard). 
PLATES 5, 6, 8, and 10 have been withheld from publication to prevent delay in the 
issue of the annual report. They will be used to illustrate a forthcom- 
ing bulletin on butter and fats, 
