_Mr. Muller's Process._--MR. SISSON inquires for any one's experience in
the use of the above formula, and I beg to say I remember when it was
published I tried it, but gave it up. It is an excellent plan, but requires
improvement. The following were my objections:
If the objects are not well illuminated by the sun, the image is not sharp.
The skies taken are singularly the reverse of the iodide-of-potash method,
as they are almost transparent.
The solutions of iron are a constant trouble by precipitating.
It has the same disadvantages as other modes on paper from inequality in
the strength of the image. The photographic _pons asinorum_ appears however
to be got over by the process, viz. taking the picture at once in the
camera, and it is very possible that it can be made perfect. A small
quantity of chromate of potash, about one grain to three ounces of solution
of iodide of iron, gives a little more force to the picture.
I find the nitrate of lead a very useful salt in iodizing paper. Six grains
of the salt to the ounce of water, and tincture of iodine added till a pale
yellow, will give additional sensitiveness to iodized paper, if the sheets
are floated upon the solution. This will shorten the time in the camera
nearly five minutes; but it requires care, as it is apt to solarize.
A weak solution of iodide of iron has also the same effect, and, if blotted
off at once, it will not blacken by the use of gallic acid.