METOL (Pr. and Ger., Metol) A salt, generally the sulphate, of methyl paramidophenol (OH)(NH according to Andresen, and of methylparamidometa cresol Co according to Hauff. It is a white, greyish or pinkish-white powder easily soluble in water. When mixed with an alkali it forms an energetic developer.
bromide) is often advisable. Sodium hypo sulphite may be used with caution in any metol developer, and Eder recommends the addition of from 2 to 4 per cent. of a ro per cent. solution for obtaining great contrasts and preventing fog.
Metol is largely used in combination with pyrogallic acid, hydroquinone, glycine and other developers, and formula; for these combined On account of the rapid appearance of the image there is a risk of taking the negative from the developer too soon. In accordance with the factorial system of development a negative developed with metol must be allowed to remain in the developer about thirty times as long as the image takes to appear, and density will then be assured. The table given above includes formulae for one-solution developers, and the formulae here given are for two-solution developers:— Two-solution Developers (Andresen) A. Metol . . . r8o grs. zo g.
Sodium sulphite . 3 oz. 195 „ Water . . . zo „ r,000 ccs.
B. Sodium carbonate 56o grs. 64 g.
Water . . . 20 OZ. 1,000 ccs. For use, take r part of A and 3 parts of B.
(Haug) A. Metol . 13o grs. is g. Sodium sulphite 3 oz. 7o grs. 173 „ Water . . . zo oz. 1,00o ccs.
B. Sodium carbonate 3 oz. 7o grs. 173 g.
Potassium bromide 14 grs. 1.6 „ Water . . . zo oz. i,000 ccs.
With regard to Hauff's two-solution de veloper above, for normal exposures and quick and vigorous development, take equal parts of A and B ; but for slow development take equal parts of A, B, and water, and add to each 3i oz. of mixed developer, 5 to ro drops
of either a ro per cent. solution of potassium bromide, or of a ro per cent. solution of sodium hyposulphite. When using this modified developer density and detail (surface and depth) develop approximately simultaneously. The addition of a few drops of citric acid (which is a more powerful restrainer than potassium mixtures will be found under the heading " Developers, Mixed," as well as, in the case of metol-hydroquinone, in the table which is given above.
Metol has an irritating effect upon some skins, and it is, therefore, wise not to wet the fingers with the developer more than is necessary. The irritation is sometimes felt when metol is used for the first time, but generally it is not experienced until metol has been used frequently over a long period. It is wise to discard metol immediately the trouble occurs, as the pain and inconvenience are likely to increase every time the metol is used. The hands should always be washed with warm water and soap, preferably carbolic, after using metol, and wiped with a dry, soft towel. Many remedies for the disease have been recommended, such as rubbing the fingers with lemon juice, vaseline, cold cream, etc., when the itching is first felt. An ointment (to be made up by a chemist) specially recommended is : Mercuric nitrate . 6o grs. 6o g.
Carbolic acid . . ro mins. ro ccs.
Zinc oxide . . 3o grs. 3o g.
Lanoline . 1 oz. ), The fingers should be smeared with the above at night, and an old pair of kid gloves worn. Coal-tar ointment is also recommended.