Page 29

MODERN DEVELOPERS

439

First: Metol is insoluble in alcohol. Paramidophenol-hydroch lor ide and hydroquinone are both completely soluble in alcohol. Inasmuch as metol substitutes are frequently cheapened, and their developing power lessened, by the addition of one or both of these, this test for the purity of metol may be profitable. A weighed sample of "metol" is well shaken in ten parts of alcohol, the residue caught on a filter paper and weighed again when dry. Any loss of weight shows adulteration. Any chemical sold as metol which is soluble in alcohol may be condemned at once. The bichromate of ammonia test is BicÂĽ::-te not s<? simJ?le but ~s of the highe~t value, espec1ally m making comparative tests with a known sample of pure metol. First prepare a 10 per cent solution of ammonium bichromate, and a solution of IO grains to each OUnce of water of each sample of metol to be tested. Now take a sheet of clean white blotting paper, such as World Photo Finish, and pour about half a dram of each solution to be tested on different parts of the blotter. Then drop one drop of the bichromate solution {by the aid of a medicine dropper) on each wet surface. With pure metol solution, a dark, purple-black ring will form at once, with a yellowcolored center, requiring several minutes for the yellow color to darken by oxidation. With impure metol or substitute, the center of the ring will immediately turn dark and the edges will not be clearly defined. Mention has already been made of the Paramido- property possessed by paramidophenol phenol: of acting as an acid with strong alkalies. Phenolate Compounds Andresen observes that by replacing the hydrogen atom of the OH grou~ee figure 12, page 423-by an alkali metal such as sodium, a phenolate compound results, e.g. of the composition CeHâ&#x20AC;˘ ONaNH,, which we may call sodium paramidophenolate. In practice this -NHs sort of compound is formed when a solution of caustic soda is added to a solution of paramidophenol- hydrochloride. Alcohol Teat

o¡

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

Advertisement