Paper developers brown-black

For brown blacks dilute 1 7 and develop for 2 to 3 minutes and 4 to 6 minutes with slow chlorobromide papers. 

Without dilution this developer will produce brown-black tones on papers in about 2 minutes. Diluted 1 2, this developer produces brown tones in 4-8 minutes. Diluting 1 4, and developing 8 to 15 minutes, produces a red-brown tone. Diluting 1 6, and developing from 15 to 25 minutes, will produce a red tone. For still warmer tones, add 10.0 grams of sodium bicarbonate to each liter of the diluted developer. 

Paper, like film, has grain, though unlike film, paper grain is not visible to the eye. Paper grains start out very small but become larger as development proceeds. When the grain first starts to develop it is yellow in color, and then turns reddish, then brown, and with full development it becomes black. 

In almost all instances the tonal quality will be improved. The resulting image will exhibit either a rich, warm brown or a finer black than was originally obtained during development. The degree to which this effect is achieved depends upon the type of developer, the strength of the intensifier, and the paper used. 

This developer will produce a variety of brown to warm black tones on various papers, depending on dilution and exposure time. 

One controversial issue in the literature concerns the toxicity of one species Panaeolus foenisecii (Pers. Fr.) Kuhn. This species has previously been classified as Psilocybe as well as Psathyrella, and has been described as Panaeolina in contrast to Panaeolus, because it is a species that does not grow on dung, fruits only after the hay harvest, and develops spores that are purplish-brown and abrasive. Other Panaeolus species, however, have black spore prints when placed on white paper underneath a glass vessel to prevent dehydration. But, even the spores oiPanaeolus foenscecii (Pers..-Fr.) Kuhn.do not all ripen at the same time, which can cause the gills to appear mottled. 

Procedure. A drop of concentrated hydriodic acid (or concentrated potassium iodide solution plus a drop of concentrated hydrochloric acid) is placed on filter paper and a drop of the acid test solution is placed in the middle of the moist fleck. The black-brown stain that develops is completely decolorized by a drop of 5 % sodium thiosulfate if no selenium is present otherwise a red-brown fleck of selenium is left. 

Procedure. A micro test tube is used. A tiny amount of the test material or a drop of its solution is mixed with several eg of calcium oxalate and taken to dryness if need be. The test tube is fastened in a perforated asbestos board and the mouth of the tube is covered with a disk of lead acetate paper. The bottom of the tube is heated to redness with a bare flame. The evolution of HgS starts when the mixture assumes a dark hue, a change attributable to the liberation of carbon during the disproportionation 2 CO -> COg -f- C. A positive response is indicated by the development of a black or brown stain on the reagent paper. 

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