68 REPORT—1850. 
chloride of sodium before seeking for fluorine, and to avoid the risk of introducing 
the substance sought for, by the employment of reagents which might possibly con- 
tain it: I effected the removal of the chloride of sodium by simply digesting the 
ashes in a minimum of distilled water. This risked the removal of a little fluoride of 
calcium or any other soluble fluoride which might be present, but precluded the 
possibility of any such compound being added to the ashes. After being washed ac- 
cordingly they were simply dried and warmed with oil of vitriol, in a lead basin 
covered by a square of waxed plate glass, which had the words “ Blood, 5th July 
1850,” traced on it by a blunt style in the ordinary way. The whole of the ashes 
was employed, but as the vessel could not contain the entire quantity, it was divided 
into two portions, the first of which remained for five days in the basin and was then re- 
placed by the other half. The glass was thus exposed for ten days continuously to 
the vapour arising from the acidified ashes. They effervesced very slightly when 
treated with sulphuric acid, but evolved a sharp acid odour. The lead vessel was 
kept at a temperature of about 150° Fahr. during the day, and fresh quantities of 
oil of vitriol were added at considerable intervals, and the contents of the basin occa- 
sionally stirred. The glass, which was cooled on the upper surface by the frequent 
renewal of a stratum of cold water, slowly became dim, and slightly opalescent where 
the letters were traced, in consequence no doubt of the separation of silica, for the 
letters appeared deeply etched when the wax was cleaned off. From the large scale on 
which the experiment was conducted, and the simplicity of the process followed, the 
evidence in favour of the presence of fluorine in the blood of the Ox seems unex- 
ceptionable; and, it cannot be doubted that the blood of other animals will be found 
to contain the same element. I presume it to be present in the state of fluoride of cal- 
cium, and that its amount is very small, but I have not attempted its quantitative 
determination. 
Milk was examined in a similar way, but its reduction to ashes was much more 
easily effected than that of blood. I failed however to obtain other than the faintest 
indications of fluorine from the ashes of about twenty imperial pints of cows’ milk. 
It was from a town dairy, and left a suspiciously-small residue of solid matter. The 
main cause of the failure however I believe to have been, the neglect to deprive the 
milk ashes of the chlorides they contained. The experiment was repeated with nine 
imperial pints of rich milk from a country farm, the ashes of which were washed with 
a minimum of water and then dried and treated like those of blood. The vapour 
which they evolved etched glass distinctly. The ashes of 12 lbs. of new skim-milk 
cheese, made this spring, treated in the same way, occasioned deep etching of glass. 
The ashes of four imperial pints of whey, treated in the same way, have barely marked — 
glass, so as to show the faintest outlines when breathed upon. Jn all probability the 
fluoride of calcium is associated with the phosphate of lime, and when milk is coagu- 
lated, separates along with the caseine. 
Fluorine was long ago detected in another of the animal fluids, as well as in the 
skeletons, both external and internal, of all classes of animals. Some difficulty was 
found at one time in accounting for the presence of fluorine in the animal tissues and 
secretions. But when we learn that fluoride of calcium is soluble in water, and is 
present in many natural waters, and that it or some other salt of fluorine exists in the 
two great formative liquids of the animal organism, milk and blood, we shall cease to 
wonder at its presence in the animal solids and fluids and begin to inquire what its 
function may be. 
The author added, in conclusion, some suggestions to chemists who desire to con- 
tinue the investigation. 
On the extent to which Fluoride of Calcium is soluble in Water at 60° F. 
By Grorce Witson, M.D., F.RS.E. 
The author, referring to his previous experiments on this subject, and taking into 
consideration the possibility of silicon having been present in some form, thought it 
well accordingly to repeat the results with solutions made in metallic vessels, and 
never allowed to come in contact with silica in any shape. 
One set of trials was made last summer in the following way :—Well-crystallized 
transparent fluor-spar was boiled for some hours in a platinum basin with pure hy- 
drochloric acid, so as to secure the conversion of any silica possibly present into fluo- 
