MINERALOGY: G. P. MERRILL 
177 
trated sulphuric acid in a small flask heated to 200°C. in a paraffine bath, the 
process being continued foffour to five hours. The gases evolved are bubbled 
through water, the fluorine being retained in water solution (in a U tube). In 
ordinary work it is customary to titrate the solution thus obtained with a 
standard alkali, but inasmuch as the meteoric samples tested contained both 
chlorides and sulphides, which would yield hydrochloric acid and sulphur 
dioxide, it was necessary to make the solution first alkaline with sodium 
hydroxide and evaporate nearly to dryness in a platinum dish on the water 
bath, the resulting concentrated solution being then added to a standard peroxi- 
dized titanium solution in a colorimeter. Fluorine has the power of de- 
colorizing or at least reducing the intense yellow color of this titanium solu- 
tion, even when present to an amount not exceeding 0.001%. 
Three samples were tested — Bluff, Texas; Allegan, Michigan; and Waconda, 
Kansas, in each of which phosphoric acid (P2O5) to the amount of 0.25% has 
been recorded, and in all of which the phosphate had been recognized micro- 
scopically. Amounts of from 10 to 20 grams were used in the tests, and in 
not a single instance did the titanium solution show the least sign of the 
presence of fluorine. It would seem safe to assume, then, that in these cases 
at least the element was not present. 
2. Further Tests for Tin in Meteorites. — It will be recalled that in my re- 
port on previous investigations, I stated that no traces of tin had thus far 
been found by us. Incited, however, by the work of Derby 3 1 was led to fol- 
low up the matter still further. Derby, it will be remembered, reported 
1.18% tin in the schreibersite of the Canon Diablo iron. Concerning this, he 
states, "Tin has not been reported (i.e., previously) possibly because the solu- 
tion has usually been made in aqua regia in which it would only appear through 
a special research. In the present case, the solution was made in plain nitric 
acid and the tin appeared as oxide and was verified by blowpipe tests." 
Having obtained a considerable quantity of material, chiefly schreibersite 
and cohenite with some carbon from various digestions of the Canon Diablo 
iron in dilute hydrochloric acid, I submitted it to Dr. Whitfield with the 
request that he examine the same with no other end in view than the deter- 
mining of tin, if present. The results were negative. Two lots of 5 grams 
each were taken and dissolved in nitric acid as described by Derby. Not a 
trace of tin could be found, either in the first solution, as oxide, or by treating 
the solution with hydrogen sulphide, in the customary way. 
On the assumption that there is no error in Derby's work, we must assume 
as suggested by him, that the tin does not belong to the schreibersite but to 
another mineral that is not generally distributed throughout the meteoric 
mass so that it only appears in certain portions of the residue. 
3. On Maskelynite. — In a very large proportion of the stony meteorites I 
have described, or studied, mention is made of a colorless, interstitial ma- 
terial either quite isotropic or slightly doubly refracting, with rather low index 
of refraction, which, following Tschermak and others, I have called, though 
