From the weight of the latter the arsenic
sulphide is calculated. As a less accurate but more rapid method, the
ammoniacal solution of arsenic sulphide is cautiously neutralized with
pure dilute nitric acid and considerably diluted. It is then titrated
with decinormal silver nitrate till a drop of the solution is turned
brown with neutral chromate. The arsenic is easily calculated from the
quantity of silver nitrate consumed. For very rough determinations it is
sufficient to treat ten grms. of finely-ground sulphur with nitric acid,
to extract with ammonia, and to add silver nitrate. From the intensity
of the color, or the quantity of the precipitate of silver sulphide,
it may be judged if the sulphur is approximately free from arsenic or
strongly contaminated. The author states that, contrary to the general
belief, reddish yellow sulphur is more free from arsenic than such as is
of a full yellow color.
* * * * *
HOW TO PLANT TREES.
By N. ROBERTSON, Government Grounds, Ottawa.
A great deal has been written and said about tree planting. Some advise
one way, some another. I will give you my method, with which I have been
very successful, and, as it differs somewhat from the usual mode, may be
interesting to some of your readers.
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