J. L. Smith— Determination of Phosphorus m Iron. 319 
1 or 2em. of ammonia acetate solution; finally, the 8 or 
10 c. m. of original solution remaining in the graduated glass 
is added with 200 or 300 c. m. of water. 
The whole contents of the large capsule is boiled gently 
from one-half to one hour, and if necessary the water renewed 
as it is evaporated. The result is the formation of a basic per- 
salt of iron containing practically all the phosphorus that was 
originally in the gram of iron used. 
Separation of the phosphorus from the above precipitate.—W ith 
a filter-pump on a 84-inch filter, the last precipitate is collected 
in 15 or 20 minutes; the precipitate is not washed, but a mix- 
ture of 5 or 6c. m. of chlorhydric acid, with an equal quantity 
of water, is warmed in the capsule in which the boiling has taken 
i i ot 
a 
this solution is placed in a porcelain capsule and evaporated to 
dryness over a water-bath or on a hot plate. I prefer the for- 
mer, although it takes a longer time. To the dry, but not 
over-heated residue is added 1 to 2 c. m. of nitric acid, with an 
equal quantity of water; this will furnish a clear solution if 
here be no titanium in the iron; if the latter be present, there 
will be formed a flocculent precipitate that can be readily sep- 
10 or 20 ¢. m., to which ammonia is to be added until the pre- 
minutes to a temperature of 80° C., and agitated with a glass 
rod. The phosphorus is precipitated as the double ammonia- 
* Whenever I filter a participate to be weighed on the filter, a double filter is 
used, each of the same size; they are weighed one against the other and exactly 
the number of mg. that it is lighter than the other. As only a 24 or 3-inch 
filter is used, the difference in weight between the filters does not usually exceed 
10 or 20 mg. I always keep a number of tliese double filters (with the difference 
marked on them) ready for this purpose or any other. 
