3156. Photographic Impressions With Fuchsine

3156.      Photographic Impressions With Fuchsine. A piece of linen goods colored with fuchsine, and dried, was exposed to the light under a photographic negative, when the image of the plate became visible on the goods, the picture looking greyish and faded where the lights were strongest. Still the picture was rather weak, and the goods were soaked for 2 days in a bath of sulphate of copper, when the picture was found to be more developed. After several rinsings in water, and two days' exposure on the grass, the rest of the goods were bleached white, leaving the picture of a pure violet tint on a white background.

3157. Tapioca Paper

3157.     Tapioca Paper. To prepare tapioca paper, which is very useful for copying photographs by artificial light, 200 grammes (61/2 Troy ounces) of tapioca are soaked for 2 days in an equal weight of water ; 10 litres (about 21 pints) of water are added, and afterwards, for every litre (quart) of liquid, 10 grammes (154 grains) iodide of potassium, 30 grammes (463 grains) chloride of potassium, 1 gramme (151/2 grains) bromide of potassium, are dissolved, and the whole boiled for 10 minutes, allowed to stand for a day, and decanted and filtered through fine linen. The paper is immersed, 12 or 20 sheets at a time - or can be floated upon it - for 15 to 20 minutes ; it is then hung up to dry in a dark room. If it has assumed a dark color, that is of no consequence, as it disappears in the silver bath. This is to be prepared in the proportion of 1 ounce nitrate of silver, 50 to 60 grains of citric acid in 30 ounces of water. The time of exposure varies from 10 seconds to 25 minutes, according to the picture to be copied and the actinic force of the light.

3158. To Recover Gold and Silver from Photographic Solutions

3158. To Recover Gold and Silver from Photographic Solutions. The silver and gold waste that result from photographic operations are best collected in a large bottle or jar, together with anything else that might contain either of the two metals. "When the bottle is nearly full, pour a little hydrochloric acid and a solution of green sulphate of iron (copperas) into it, and let it stand on a warm place until the supernatant liquid appears perfectly clear. Add then a few drops more of the hydrochloric acid and iron solution, and observe whether a fresh precipitate forms or not. In the latter case, draw the clear liquid off by mean* of a syphon, and reserve the residue. If the bottle has become partially filled in course of time with insoluble chloride of silver and metallic gold, place the residue on a filter, wash it with very dilute acid, and, lastly, with water. After drying, it is to be mixed with several times its weight of dry carbonate of soda, the whole conveyed to a crucible, and the latter heated to a bright red heat, and kept there for about 10 minutes. After taking the crucible out of the fire, and allowing it to grow cold, it is broken, the button of the alloy of gold and silver cleaned, and heated in a suitable vessel with dilute nitric acid, which will dissolve all the silver, as nitrate of silver, and leave the gold in a finely divided state. This is dissolved by nitro-hydrochloric acid (aqua regia). It is hardly necessary to say that, for photographic purposes, both solutions must be evaporated in a water-bath until the excess of acid has been volatilized, when they may be diluted with a sufficient amount of water, and used. (See No. 3166 (To Recover Silver from Photographic Waste).)