1895.] Fluorine as a Test for the Fossilization of Animal Bones. 309 
will arrest sulphuretted hydrogen when the calcined matter 
contains a sulphide which is decomposed by sulphuric acid. 
If there be organic matter which can evolve sulphurous acid, 
the latter can be retained by the use of caustic lime freshly 
calcined. In the case of substances containing iodine, it is 
moved by means of the copper turnings placed before the sul- 
phate of copper. In determining fluorine, 5 grams of the ash 
of modern bones to 2 grams of fossil bones are employed in 
such way as to always have a convenient quantity of fluosili- 
cate of potassium to determine on the balance. 
2. Chlorine—For the determination of chlorine a special 
operation is performed, treating one or two grams of ash by 
cold nitric acid slightly diluted. When the solution is com- 
plete, we add water and nitrate of silver. The weight of chlo- 
ride of silver dried, will give the proportion of chlorine. 
3. Carbonic Acid—The proportion of carbonic acid enabling 
us to calculate the carbonate of lime is obtained by attacking 
from two to four grams of ash by nitric acid in a small flask 
exactly weighed and provided with a tube containing pumice 
saturated with sulphuric acid (pawnce) to retain humidity. At 
the end of the operation, the carbonic acid is replaced by dry 
air by aspiration, and the apparatus is weighed. The loss of 
weight represents the carbonic acid disengaged. 
4. Phosphoric Acid, Lime, Magnesia, Alumina, and Oxide of 
Iron.—Two grams of ash are used in this operation. Dissolve 
in hydrochloric acid and heat in a capsule of platinum a suffi- 
cient length of time to drive out the fluorine. The solution di- 
luted with water, is then filtered, afterwards saturated by am- 
monia until the commencement of precipitation of phosphate 
of lime, then redissolved by acetic acid added little by little in 
slight excess in such a manner as not to produce a noticeable 
heating of the liquid. 
Phosphate of iron is precipitated in this way alone or with 
phosphate of aluminum. If this precipitate is almost insig- 
nificant, we take the weight after washing and ignition and 
according as (1) the absence or (2) the presence of aluminum 
is observed, we calculate by the following formula the weight 
