The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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of a 50 per cent, solution of sodium hydrate and diluted with 60 of water. Developer 5. - Equal bulks of these solutions are mixed immediately before use. It resembles Developer 4 in its action. Acetic acid and acetates act strongly as restrainers, yellow prussiate of potash acts as an accelerator. The great fault with incautious use of hydroquinone is that one is very liable to obtain negatives with very great contrasts.
Hydrotype. A kind of reversed collotype. (See Collo-type.) The plate is exposed under a positive, and the gelatine is allowed to swell in a coloured solution; a printing surface being thus obtained which.will yield impressions on paper.
Hydroxyl, Hydroxyl Monohydride. See Hydrogen Per-oxide ; also Hydrates.
Hydroxylamine Hydrochlorate (Ger., Salzsdures Hydro-xylamin; Fr., Chlorhydrate d'hydroxylamifie; Ital., Chloridrato dHdrossilimind). NH2.OH.HCl. Prepared by the reduction of nitrite and nitrate of ammonia. It is very soluble in water and alcohol; it has been recommended as a new developing agent; its price is at present against it, but recent improvements in the manufacture provide hope of a speedy reduction in price. It is absolutely non-staining, but is subject to the disadvantage that it causes the film to blister by the disengagement of nitrogen. It has, however, been stated that this can be prevented by adding thiosinnamine or glucose to the developer. The following is the form recommended by Messrs. Egli & Spiller: -
Hydroxylamine Citric acid Distilled water
II. Carbonate of potash Carbonate of soda ... Distilled water
32 grs. ... 15 .. 1 oz.
... 480 grs. ... 480 .. 10 ozs.
Solution I..........        ...        ...      30 mins.
Solution II. ...        ...        .:.        ...        ...     120 ,,
Distilled water ... ...        ...        ... oz.