162. The value of permanganate of potash for rectifying disordered negative baths and printing baths has received much confirmation during the past year. A correspondent of of the journals describes his experience thus:
Permanganate of Potash,........................................................................
"I poured into my bath about a teaspoonful of the above. In one minute it had the appearance of very dirty ink. I filtered it, after which it looked very yellow; I dropped in a tittle more of the permanganate, and set it in the sun for ten minutes. It then assumed a clear, bright, pink appearance; I filtered again, and again set the solution in the sun. In fifteen minutes the excess of permanganate had precipitated in the shape of a black, gummy-looking may be used, or nitrate of barytes often found helpful. The per-manganate of potash is also resoted with good results. The choice of these should depend upon circumstances and conditions, though their action is much alike.
163. In handling; a bah solution, much waste may occur if the operator is not careful in pouring the solution to and from the bath - holder. A siphon may be used for the larger solutions with greater assurance against accident and loss. With, care, no loss need necessarily occur by either method.
164. One of the gentlest means of curing a disordered bath is by givmatter. I coated a plate, and placed my subject, exposed, developed, and the nicest chemical effect I had ever seen was the result. I have worked that bath for six weeks with all sorts of collodions, and only once has it given a foggy picture; then a few drops of the permanganate set it right."
Another correspondent, speaking of its use in printing-baths, says, " I proceed as follows:
Dissolve the permanganate in water, and add with caution to the old bath until you obtain a milky - purplish color; let it remain over night, after giving it a thorough shaking. You will find quite a large amount of foul matter has fallen during the night. The solution can now be filtered nearly clear. Now proceed as with an old negative bath, which is, to add the solution of permanganate of potash as above to this filtered solution until you obtain a stronk pink color; let it remain for a few hours, after stirring well before filtering; if quite alkaline, add nitric acid until it turns litmus-paper pretty deeply red, then aqua ammonia until it is as alkaline as you usually use your bath." - G. Wharton Si carbonate of soda. In a few hours a black scum will be found on the surface of the bath. This can readily be removed by a strip of blotting-paper, and the solution is again free to the action of the sunlight. This should be repeated every few hours until the bath remains, clear, or nearly so, when it is ready to be filtered and diluted by the addition of water, for, as will be readily understood, during the process of sunning in a flat, open dish, there has been considerable evaporation of both water, alcohol, and ether. After being diluted, filtered, and acidified, it will be found to work as well as ever it did, free from streaks, stains, and pinholes. The advantage of the dish over the bottle, so generally used in sunning, is, that the black scum which collects on the inner surface of the bottle obstructs the rays of the sun, and prevents the free access of light to the solution, and thus renders the process of sunning much more lengthy and tedious than when the dish is used. - J. L. Gihon.
168. The following is a good way to empty a bath - holder without wasting the contents. Simply use a white cotton string or twine, tied about an inch or so from the edge, and if the glass and twine are dry not a drop will be wasted. - J. L. Gihon.
Take any length of rubber hose, of size required for business in hand, press one end tightly on a wooden roller (almost anything will do), rolling up till just enough is left to reach in the solution; be sure you keep it there, and commence unwinding, keeping the end not in the solution held tight, pass it in the bottle or hold over the vessel used; in this way you will find the solution to pass over and out readily. I think this is more feasible than the one with glass tube intervening, but that is very good. - J. C. Goetchius.
Another thing which may be new, and therefore valuable to some of you, is, how to draw off your hath. Get a piece of rubber tubing, say four feet long, put one end in the bath and drop until all is covered Except just your finger-hold; pinch lightly, pull out, and insert in the mouth of a bottle. When that is full, pinch together until you direct into another bottle. In this way, simply by having the tubing reach the bottom of the. hath, and discharging outside at an inch or two lower, you can draw off your whole bath without much trouble and with no waste. - N. D Randall.
164. A Wat to Sun a Bath - Pour it out into a flat porcelain dish and leave it in the sun, sheltered from the dust. The hath should first be neutralised, say with ing it a sun-bath. Many disbelieve in such treatment, but it is largely practised and is very good. It is slower than some other means used, but it is none the less sure, and is certainly not liable to accident.
165. Another method is to "boil down" the bath. The water and other fluids it contains are thus evaporated, when the silver crystals are again dissolved in water as when the bath solution was originally made. A still further method is to fuse the silver, the advantages of such a method being considered greater than those gained by simple evaporation to dryness.
I should be very sorry to show disrespect to any one whose opinion differs from mine; nor do I intend to. I only wish to express my own very forcibly in regard to "sunning" the bath. That is all bosh ! It can possibly do no harm and does some good; but half an hour's boiling is worth a year's "sunning." - Elbkrt Anderson.
165. There is a compound of silver which a photographer might unwittingly produce - the fulminate of silver. If a solution of nitrate of silver containing nitric acid be warmed, and alcohol added, a white precipitate forms, which is the compound in question. A photographer evaporating to dryness an acid bath which had long been in use, and contained alcohol, might find himself and his dishes elsewhere towards the termination of the boiling down of the solution. - Old Argentum.