Collodion, Iodine. Prep. Dissolve iodine and Canada balsam, of each 1⁄2 oz., in collodion, 1 pint. Used as a substitute for IODINE OINTMENT.
Collodion, Morphia. (L′Union Medicale.) Dissolve 1 part of hydrochlorate of morphia in 30 parts of flexible collodion, and apply with a camel-hair brush.
Collodion, Photograph′ic. 1. There are so many methods adopted for preparing photographic collodion, that a large volume might be filled with notices of them. We have retained Mr Hardwich’s forms, which were formerly much esteemed by practical photographers, and appended to them modern formulæ which are now, we believe, in much greater demand, and for which we are indebted to Mr Ernest Spon’s valuable book ‘Workshop Receipts.’
2. Pyroxylin, and iodide of cadmium, or ammonium, of each 15 gr.; ether, 31⁄2 oz.; alcohol, 11⁄2 oz. Place the two first in a dry bottle, then pour on the spirits of wine, shake the mixture well, then add the ether, shake again and let it stand for 12 hours. Decant the clear portion into a wide-mouthed bottle, keep well stoppered, and in the dark. Avoid shaking the bottle when about to use the collodion, and never quite use all the bottle contains, as the sediment which will accumulate at the bottom would spoil the picture. The preparation of a sensitive collodion, whether positive or negative, includes three distinct operations, namely, the formation of the pyroxylin or gun-cotton, the conversion of this into plain collodion, and the final process of iodising the collodion.
Collodion, Plain. Mix in a bottle gun-cotton, 450 gr.; ether, 25 oz.; spirits of wine, 7 oz. Shake these well together, and leave to settle several days. Keep well corked.
Collodion, Pos′itive. (Hardwich.) To form the PYROXYLIN:—Take sulphuric acid, sp. gr. 1·845, at 60° Fahr., 12 fl. oz.; nitric acid, sp. gr. 1·45, at 60°, 12 fl. oz.; water, 31⁄2 fl. oz.; mix, and allow the temperature to fall to 140°; then immerse cotton, 300 grains. (If the cotton is found to gelatinise or dissolve in the acid mixture, the quantity of water is too great, and may be reduced to 3 fl. oz.) The cotton should be well pulled out in pieces, weighing about 30 grains each; and should be left in the acid for about 8 minutes, the vessel being covered over. It is taken out with a glass spatula, squeezed to remove acid, washed for at least 24 hours by a stream of water, then squeezed in a cloth, and pulled out to dry. To form the PLAIN COLLODION:—Shake up the dry pyroxylin, 48 grains, with alcohol, sp. gr. ·805, 11⁄2 fl. oz., and then add ether, sp. gr. ·725, 41⁄2 fl. oz. The solution should be allowed to rest for a week or ten days, when the clear fluid should be decanted from the sediment. To prepare the IODISING SOLUTION:—Take of iodide of ammonium, 11⁄2 dr.; iodide of cadmium, 11⁄2 dr.; bromide of ammonium, 40 grains; powder, and dissolve in alcohol, sp. gr. ·805 to ·816, 10 fl. oz. The collodion is iodised by adding the solution to it in the proportion of 1 part solution to 3 parts collodion. The iodised collodion should be kept for at least six weeks before using. If required
for immediate use, add a few drops of an alcoholic solution of iodine, formed by dissolving 5 grains of iodine in 1 fl. oz. of alcohol.
Obs. Mr Hardwich recommends that the cotton, before being converted into pyroxylin, should be cleansed by boiling for two hours in a solution of caustic potassa (2 oz. to the gallon), and by being afterwards repeatedly washed and dried. The purest nitric acid, sp. gr. 1·45, should be employed, but the ordinary commercial sulphuric acid (oil of vitriol) is sufficiently pure for use. To purify the ETHER and to get rid of a certain ozonised principle which would decompose the iodising solution, Mr Hardwich recommends the following process:—Take the best washed ether of commerce and agitate it thoroughly with a small portion of dilute sulphuric acid, and then introduce it into a retort, and distil over one third. The alcohol used is of the strength of that sold for absolute alcohol; it should be pure.
Collodion, Neg′ative. (Hardwich.) To form the PYROXYLIN:—Take of sulphuric acid, sp. gr. 1·845, at 60°, 18 fl. oz.; nitric acid, sp. gr. 1·475, at 60°, 6 fl. oz.; water, 51⁄4 fl. oz.; cotton, 300 grains. Mix, and allow the temperature to fall to 150° Fahr. The weight of the pyroxylin ought to be 375 grains. To form the PLAIN COLLODION:—Take alcohol, sp. gr. ·806, 1⁄2 gallon; ether, sp. gr. ·725, 1 gall.; pyroxylin, 1900 grains. Saturate the pyroxylin with the alcohol, then pour in half a gallon of the ether, agitate for 3 or 4 minutes, and repeat the process in adding the remainder. Decant the clear liquid from the sediment after a week or ten days’ rest. The following forms for IODISING SOLUTIONS are recommended:—a. (Potassium Iodiser.) Iodide of potassium, 135 grains; alcohol, sp. gr. ·816, 10 fl. oz. Powder and dissolve in the alcohol, previously heated to 140°.—b. (Cadmium Iodiser.) Iodide of cadmium, 170 grains; alcohol, sp. gr. ·816, 10 fl. oz. Dissolve in the cold, and filter.—c. (Bromo-iodiser.) Bromide of ammonium, 40 grains; iodide of ammonium, 90 grains; iodide of cadmium, 90 grains; alcohol, sp. gr. ·816, 10 fl. oz. Pulverise and dissolve in the cold. To sensitise the collodion, add to three parts one part of either a, b, or c.
Obs. Most of the practical directions given under the head of POSITIVE COLLODION apply equally to NEGATIVE COLLODION. Nothing but patient and intelligent practice will ever lead to success in preparing collodion for photographic purposes. Although formulæ of undoubted excellence may be used, it continually happens that the results are entirely nugatory from some trifling cause. See Photography.