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Updated: June 1, 2025
Keep the camera and mercury-bath perfectly free from the vapors of iodine and bromine; for the presence of the slightest degree of either of the above will injure the impression in no small degree. As a preventive, let the camera be exposed to the sun or fire for a few minutes in the morning. Filter your mercury often, to keep the surface free from film and dust.
If a plate, coated over the iodine to a rose red, and then exposed to strong dry quick or weak bromine water, so that a change of color can be seen, then recoated over the iodine twice as long as at first coating, it will be found far more sensitive when exposed to the light than when it has been recoated over the iodine one-fourth of the time of the first coating.
I had used ammonia and bromine. I did not know it at the time, but I had made bromide of nitrogen. I put the large bulk of it in three filters, and after it had been washed and all the water had come through the filter, I opened the three filters and laid them on a hot steam plate to dry with the stuff. While I and Mr.
Here, then, we have essentially the same chemical elements that we have seen employed in the daguerreotype, namely, iodine, bromine, and silver; and by their mutual reactions in the last process we have formed the sensitive iodide and bromide of silver. The glass is now placed, still wet, in the camera, and there remains from three seconds to one or two minutes, according to circumstances.
Most experienced operators have been long acquainted with the effect of the vapor of ammonia upon the chemically coated plate. I will here insert Mr. W. H. Hewett's plan of proceeding. The effect is produced upon a simple iodized plate, but still more upon a plate prepared in the ordinary way, with both iodine and bromine.
By communicating to the vessel containing the solution a continual motion, the impression, when once immersed, will be fixed. During that time, and while attending to anything else, watch its color; and at the end of ten minutes or a quarter of an hour, take it out of the bath and dry it. Agent for Neutralizing Bromine, Chlorine, and Iodine Vapors.
"Still, I'm not sure," he continued, slapping his bald head with a bandana handkerchief, "that a whiff of chlorine or bromine wouldn't do these trenches a considerable amount of good. It would tone down some of the deceased a bit, and wipe out these infernal flies. Waddell, if I give you a shilling, will you take it over to the German trenches and ask them to drop it into the meter?"
A few drops in a large flask will fill the whole vessel when slightly warmed, with blood red vapors, which have a density of nearly 6.00, air being one. It is a non-conductor of electricity, and suffers no change of properties from heat, or any other of the imponderable agents. It dissolves slightly in water, forming a bleaching solution. Chloride of Bromine.
The principal difficulty in coating the plate, is that of preserving the exact proportion between the quantity of iodine and bromine, or quick.
It is passed into a newly-acidulated bath, rinsed, and dried. After the bromine bath has been used up, it is regenerated by adding 1 per cent. of sulphuric acid, which liberates the bromine. To the same bath caustic soda is added, which regenerates the hypobromite of soda. The hydrofluosilicic acid can be used, instead of the sulphuric acid, with greater advantage.
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