318 J. L. Smith—Determination of Phosphorus in Iron. 
all varieties of iron; for even where the iron or steel contains 
one-thousandth and less of phosphorus, I get as satisfactory 
results as where 2 and 3 grams are employed. 
ution.—The iron, say 1 gram, is placed in a porcelain 
capsule of about from 100 to 150 ¢. m., and 3 or 4c. m. of water 
added ; the capsule is placed on a water-bath, and 10 to 15. m. 
of aqua regia is added little by little; the aqua regia is prepared 
in advance in the usual way with two parts chlorhydric acid 
and one part nitric acid. The contents of the capsule are now 
evaporated to dryness over the water bath or more speedily on 
an iron plate; the capsule with its contents is then placed in 
an air-bath and heated from 140° to 150° C. for from 30 
minutes to 1 hour—thus rendering all the silica insoluble; 3 
or 4c. m. of chlorhydric acid with an equal quantity of water 
are added to the dry residue, and then warmed gently over a 
water bath or lamp; the iron is redissolved, a little more water 
added, the solution filtered with the filter pump; the filtrate 
placed on a narrow graduated measure of 100 c. m. capacity and 
sufficient water added to make the liquid contents 100 ¢. m.; the 
whole is well shaken to make the solution uniform. ‘The next 
step is to concentrate all the phosphorus into a limited amount 
of the iron. 
Concentration of the phosphorus.—From 90 to 92 ¢. m. of the 
last solution is placed in a capsule of 300 or 400 ¢. m. capacity, 
either of porcelain or platinum—the latter I use by preference 
—and ec. m. of water added; the iron oxide is now reduce 
to iron protoxide by soda sulphite or ammonia sulphite.* i 
prefer the latter, and prepare it in the manner mentioned in 
the note; the ammonia sulphite I used at the suggestion 
of Mr. S. Peters, which he stated to me was used advan- 
tageously by himself and others. wo or three centimeters 
of the ammonia sulphite is added to the iron solution and the 
contents of the capsule are boiled until all the sulphurous acid 
is driven off, this stage of the process being recognized by the 
sense of smell. By putting a small drop of the solution on 
the end of a glass stirrer into a weak ammonia solution we 
readily recognize the complete conversion of the oxide, for the 
precipitate is nearly white. Of course during the whole of the 
above process the solution. is acid, with the excess of chlorhy- 
dric acid. Ammonia is now added slowly to the warm solu- 
tion until a little of the greenish precipitate remains undis- 
solved; about 20 ¢. m. of acetic acid is now added to the solu- 
tion (which immediately redissolves the precipitate), and then 
ammonia and water are placed in a bottle and an excess of 
sulphuric acid passed through; the operation Jasts for several hours, using a m1x- 
ture of charcoal and sulphuric acid. Once prepared it keeps very well, when 
kept from the light. 
