Sensitized Collodion

Add to 1 oz. of the plain collodion 6 drs. of spirits of wine, 1 3/4 oz. of ether, and 3 drs. of iodide and bromide solution. Shake the bottle well; the mixture is then ready, but is improved by being kept 4 or 5 hours before using. In hot weather a little more alcohol, and less ether, in very cold weather more ether, and less alcohol, must be used. As sensitized collodion does not keep well, it is better not to mix the plain collodion and the iodide and bromide solution until shortly before required for use.

Iodide and Bromide Solution

Iodide cadmium 154 grs., bromide of cadmium 54 grs., spirits of wine 3 1/2 oz. Rub the iodide and bromide to fine powder in a mortar, add the spirits of wine gradually, and when the iodide and bromide are dissolved, filter through paper into a bottle. This solution will keep well in a closely-stoppered bottle.

Iodized Collodion may be made at one operation. It should be kept two days before using, but it is less reliable, if kept for any length of time, than sensitized collodion, which has been made as above described. It is made as follows. Place 16 grs. of gun-cotton in a bottle, add 18 grs. of iodide of cadmium, and 6 grs. of bromide of cadmium, in powder, and 1 1/2 oz. spirits of wine, sp. gr. 0.805. Shake the bottle till the iodide and bromide are dissolved, then add 3 oz. ether, sp. gr. 720, and shake until the cotton is dissolved. After 24 hours decant the clear portion into small well-stoppered bottles.

Nitrate of Silver Bath, for Negatives

Recrystallized nitrate of silver 1/2 oz., distilled water 7 oz., collodion 7 drops. Shake well together until the crystals have dissolved, then filter.

The purity of the negative bath is a matter of great importance, hence the necessity of employing the very best nitrate of silver, and also of excluding all foreign matters of every kind. When the bath gets out of order, it should be diluted with an equal bulk of distilled water, and exposed to the sun for a few days, in a white glass bottle, then filtered, and sufficient nitrate of silver added to restore the strength to 35 grains to an ounce, as indicated by the argentometer.

The Argentometer

This instrument is for ascertaining the strength of the nitrate of silver solution, which becomes weakened to a certain extent, after the immersion of every plate.

Developing Solution, for Negatives

Protosulphate of iron 75 grs., glacial acetic acid 2 drs., alcohol 2 drs., distilled water 5 oz. Dissolve the crystals in the water, then add the acid and alcohol, and filter. In hot weather a little more acetic acid may be added, and if it does not flow readily, the alcohol may be increased.

Intensifying Solution

No. 1 (negatives). Pyrogallic acid 10 grs., citric acid 10 grs., distilled water 5 oz. When it becomes brown it is useless. No. 2. Reerystallized nitrate of silver 40 grs., distilled water 1 oz; dissolve and filter. This latter will keep for any length of time in the dark.

Another Intensifying Bath (negatives)

A saturated solution of bichloride of mercury in water. Place the negative plate in a bath of the solution, remove when the film assumes a milky-white appearance, wash, and then plunge into a solution of 1 oz. of liquid ammonia to 10 oz. of water. Remove the plate, wash, and place to dry. This mode of intensifying may he regulated by leaving the plate in the bichloride of mercury a shorter time, when it will require a weaker ammonia bath than that above given.