potassium and proto-sulphate of iron, following the method given by Dr.
Eder for the preparation of his ferrous oxalate developer. He carried
out the development in the same way as is done by the oxalate, and
he found that the succinate of iron is even more energetic than the
oxalate. The plate develops regularly with much delicacy, and gives a
peculiar tone. It is necessary to take some fresh solution at every
operation, on account of the proto-succinate of iron being rapidly
converted into per-succinate by contact with the air.

_Method of Making Friable Hydro-Cellulose_.--At the meeting of the
Photographic Society of France, M. Girard showed his method of preparing
cellulose in a state of powder, specially adapted for the production of
pyroxyline for making collodion. Carded cotton-wool is placed in water,
acidulated with 3 per cent. of sulphuric or nitric acid, and is left
there from five to fifteen seconds; it is then taken out and laid on a
linen cloth, which is then wrung so as to extract most of the liquid. In
this condition there still remains from 30 to 40 per cent. of acidulated
water; the cotton is divided into parcels and allowed to dry in the open
air until it feels dry to the touch, though in this condition it still
contains 20 per cent. of water. It is next inclosed in a covered jar,
which is heated to a temperature of 65 deg. C.; the desiccation therefore
takes place in the closed space, and the conversion of the material
is completed in about two or three hours. In this way a very perfect
hydro-cellulose is obtained, and in the best form for producing
excellent pyroxyline.--_Corresp. Photo Mews_.

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