she and Clara admire it. So do I. I wish that your song，
Chloride of Iodine. (See page 85.)
Chloride of potassium.--or (Muriate of Potassa).--Dissolve half an ounce of carbonate of potassa in water, and neutralize with muriatic acid. Upon concentrating the solutions, cubic crystals will be obtained, having a taste similar to common salt. They consist of potassium and chloride, and when dissolved in water they may be regarded as muriate of potassa.
Chloride of Lime.--Mix half an ounce of slacked lime (hydrate of lime) with six ounces of water, and conduct into this milk of lime, with frequent agitation, as much chlorine gas as will evolve from two ounces of muriatic acid and half an ounce of black oxide of manganese. The liquid clarifies by standing; may be regarded as a solution of chloride of lime, and must be protected from the air and light. It may also be made without putting in the water with the hydrate of lime, by merely passing the chlorine into the hydrate of lime. This last is by some used in preparations for accelerating the operation of taking Daguerreotypes, but when used for this purpose it is in small quantities.
Chloride of Calcium.--To one part of water add two parts of muriatic acid, and add pieces of common chalk until effervescence ceases; then filter through cotton cloth and evaporate it by placing it in all earthen or porcelain dish, over a slow fire, to the consistency of a syrup. When cooling, large prismatic crystals of chloride of calcium are formed. These must be quickly dried by pressing between folds of blotting paper and kept carefully excluded from the air, as it readily attracts hydrogen. For most daguerreotype purposes, the syrup may be at once evaporated to dryness. This is frequently placed in the iodine coating box for the purpose of keeping the atmosphere dry. It is so easily made that every operator can provide himself with it in a short time, and at little expense.
Chloride of Gold.--Is prepared by dissolving gold in aqua regia, a composition of one part of nitric to two parts of muriatic acid. Gold foil is the best for our purposes; coin, however, answers, in most cases, for the daguerreotype operator, as the alloy, being so slight is not noticed in the gilding process. When the latter is used, it will facilitate the operation to beat it out, forming a thin sheet, and then cutting in small strips. Where purity is required, foil is better. The gold is placed in three or four times its own weight of the above acids. For this purpose, an evaporating dish is best (a common saucer will do); a moderate heat may be applied to favor the action. The mixture should be stirred often with a glass rod; care should be observed not to apply too much heat, for at a temperature of about 300 deg. the chlorine would be expelled and leave a metallic precipitate, which would require re-dissolving. Acid may at any time be added if necessary to dissolve the gold, but it is advisable to add as little excess as possible, as it would require more time to evaporate. After all the gold has dissolved, and the liquid assumes a deep red color, the solution should be allowed to cool, being stirred nearly all the time. This salt is of a reddish-brown color. It is rarely we find in our market good chloride of gold, as common, salt is used for the bulk; and when the bottles are labelled "15 grains," "20 grains," nine-tenths do not in reality contain exceeding five grains of chloride of gold. The salt is mixed with the above solution when it is cooling, and gives bright yellow crystals, which some of our uninformed operators conceive to be the best quality.
Chloride of Silver.--(Oxide of Silver.)--Take any quantity of silver coin or other silver, roll or hammer it thin; cut in small pieces. This in order to save time. Put the silver in a glass or earthen vessel (Florence flask is best); pour in nitric acid and water, about three parts of the former to one of the latter. The operation of cutting up the silver may be facilitated by applying a gentle heat. This blue solution consists of oxide of silver and oxide of copper, both combined with nitric acid. Should the operator wish a pure solution of silver, which, however, is not always used, he may obtain it in the following manner:
To separate the two metals contained in the above solution from each other, put some bright copper coins into the solution and set it aside in a warm place for three or four days, occasionally giving it a circular motion. The separated laminae are pure silver, which is to be digested with ammonia until it ceases to be colored blue. The silver, after being washed and dried, is again dissolved in nitric acid, and the liquid, diluted with water, is kept as solution, of silver.
Either of the above solutions (the one of oxide of silver and copper, and the pure silver solution) may be prepared for use by putting them in a bottle, with a quantity of water, and adding common fine salt, you obtain a white curdy precipitate of chloride of silver. No matter how much salt is used, provided enough be added to throw down all the chloride of silver. This solution should be well agitated and then allowed to stand for a few minutes; thus the white precipitate is in the bottom of the bottle. When the water has become clear, pour it off with care, leaving the sediment behind, then add a fresh quantity of clean water, shake, let settle, and pour off as before. Repeat the same for several times, and the excess of salt will disappear, leaving the white precipitate, which may be drained of the water and dried in the dark, and kept free from light and air.
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