METOL. (Formula: H„ NO.) Metol is the trade name given to the sulphate* of methyl paramidometacresol. It takes the form of a whitish powder soluble in water. A solution of it with alkalies in presence of alkaline sulphites will remain colorless for a great length of time. Employed with alkaline carbonates it forms a very energetic developer for gelatino-bromide dry plates, or in a more diluted form it can be used for gelatino-chlorida, or chloro-bromide gelatine plates.
Instead of the potassium carbonate 120 parts of crystallized sodium carbonate can be used. For portrait work this solution is diluted with an equal volume of water and for landscape work, with twice its volume of water.
For use, mix three parts of A with one part of B. Development is usually complete in three minutes. For slow development and soft images use more water and less alkali.
For use, add to zoo parts of water 20 parts of A and zo parts of B.
The soda developer works slower than the potash, but both are suitable for portrait or landscape work. Potassium bromide acts as a restrainer though not so powerfully as with other developers, nor does it so much tend to produce hard images. Old developers can be used in cases of over exposure. The same developer can be used for development of several plates.
Even after use it remains almost colorless for a long time. The image usually appears very rapidly with all its details and gains opacity afterwards.
Metol solutions have the effect of hardening the gelatine film so that a longer time is required for fixing. According to Larsoff, after the image has appeared, the film, while in the metol solution, is practically insensitive to white light, although the solution itself is colorless and transparent.
Metol can also be used for the development of positives on bromide paper. For this purpose Dr. Just recommends three stock solutions : Water zoo parts Metol z part Sodium sulphite zo parts Water Too parts Potassium or sodium carbonate lo parts Water zoo parts Potassium bromide zo parts For sepia tones: Water, 84 parts; solution A, 6 parts; B, z part: C, a few drops. For red tones use 140 parts of water and more of C. For black tones give short exposures and use 6o of A to 10 of B and a few drops of C.
According to Col. Waprhouse old metol solutions can be detected by the decided and unmistakable smell of phosphorus they evolve.