Читать книгу A Practical Manual of the Collodion Process. Giving in Detail a Method For Producing Positive and Negative Pictures on Glass and Paper онлайн

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Before concluding the subject on plain collodion, I will introduce the account given by Mr. E. A. Hadow of his interesting and valuable experiments, as published in Humphrey's Journal, Vol. VI, page 18.

"Having obtained good collodion-wool, the next point of inquiry was with regard to the solvent; to ascertain whether the addition of alcohol beyond what is necessary to cause the solution of the gun-cotton in ether, were beneficial or otherwise. For this purpose ether and alcohol were prepared perfectly pure, and mixtures were made of 1 of alcohol to 7 of ether, 2 to 6, 3 to 5, 4 to 4 and 5 to 3. In one ounce of each were dissolved 6 grains of gun-cotton and 4 grains of iodide of ammonium (iodide of potassium could not be employed, since it requires a certain amount both of water and alcohol to keep it in solution); they were then compared, using a 35-grain solution of nitrate of silver, both by pouring on separate glasses, and likewise by covering two halves of a plate with two samples, as in examining the gun cottons, thus placing them under the same circumstances during the same time; in this way the effect of adding alcohol was very clearly perceived, since the difference between the collodions was much greater than could have been anticipated.