The Art and Practice of Silver Printing

be followed as a whole, instead of being studied in fragments, a course which is sure to lead to failure, from a want of comprehending what may have been skipped. To understand "the why" and "the w

ch a manner that everyone will be able to understand them, provided only that there is

ARY EXPE

f pinches of common salt, which mu

pour a little common salt solution, and on the other two pour a little solution of silver nitrate; take one of each pair, and place it in a dark cupboard (if warmed, the quicker will be the operation) to dry. Take the other two moist portions of chloride into the open air, and expose them to daylight, and note the results. It will be seen that one of these will darken very rapidly to a violet colour, whilst the other will remain much lighter, though perceptibly blackening. After a time the latter will appear to grow deeper, w

(by which are meant such bodies as chlorine, iodine, bromine, and fluorine). In the former case we have silver chloride formed with a little hypo-ch

ome as above, well wash it, and expose it to light in pure water, we shall find that the latter contain

salt, there will be hardly any discolouration. The experimentalist should also note that if the darkened chloride be broken up, the interior retains its white colour in all its purity. This tells us that

y) as compared with that which is darkened in contact with the potassium nitrite. We have the best of reasons for believing that the blue colour is really due to a combination betwe

ter it. Pour a little of the filtered albumen (the white of egg) into a test-tube, and add a little silver nitrate solution to it, and expose the precipitate which falls to light. It will be seen that it darkens rapidly, assuming a foxy red colour. Take a couple of glass plates and coat them with plain collodion, wash under the tap, and whilst still moist flow albumen over them two or three times, and set them up to dry. When thoroughly dry, plunge th

ome papers, we shall find very much the same nature of things taking place,

reat the darkened silver chloride solution exposed with the silver nitrate or the potassium nitrite to a solution of hyposulphite of soda or ammonia, both of which are solvents of the white chlor

n (sulphuretted hydrogen[5]). It will be found that the colour of the darkened silver chloride becomes more intense, while the other is bleached, or, rather, becomes of a