. The silver sunbeam : a practical and theoretical text-book on sun drawing and photographic printing. CHAPTEE LXIII. ORGANIC DEVELOPERS. There have been used many developers compounded ofthe ordinary salt of iron and different organic matters. Oneof the best of these is made as follows : Make a solution ofgelatin, ten grains to the ounce of water, and a solution of tan-nin, fifteen grains to the ounce of water. While the gelatinsolution is warm, add to it three drops of the tannin solution,and mix thoroughly. Add one drop of this mixture to each Fig. ounce of the ordinary developer. This
. The silver sunbeam : a practical and theoretical text-book on sun drawing and photographic printing. CHAPTEE LXIII. ORGANIC DEVELOPERS. There have been used many developers compounded ofthe ordinary salt of iron and different organic matters. Oneof the best of these is made as follows : Make a solution ofgelatin, ten grains to the ounce of water, and a solution of tan-nin, fifteen grains to the ounce of water. While the gelatinsolution is warm, add to it three drops of the tannin solution,and mix thoroughly. Add one drop of this mixture to each Fig. ounce of the ordinary developer. This slight addition makesa remarkable difference in the action of the developer, andenables one to use it over and over again merely by filtering. Instead of gelatin, various other organic matters can beused with the tannin, viz., starch, tapioca, gum Arabic, etc. Another excellent developer is compounded as follows : Double sulphate of iron and ammonia, ... 4 ounces. Rock candy, | ounce. Water, 64 ounces. Acetic acid, No. 8, 4 538 DEVELOPING. An excellent developer for ferrotypes is made as follows :Prepare a saturated solution of protosulphate of iron, alsodissolve two grains of tannin in an ounce of alcohol. Addgradually of the tannin solution to that of iron until the lat-ter ceases to redissolve the precipitate formed. Then add aFiff 9 very little nitric acid to redissolve the the solution by theaddition of twelve times itsbulk of water. Now, byadding to each ounce abouthalf the quantity of aceticacid ordinarily used, the de-ve
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