ADUROL (Fr. and Ger., A durol) A developer intermediate in character between the short factor developers, such as pyro and hydroquiuone, and the longer factor developers such as metal, rodinal, amidol, etc. ; introduced in 1899. It is a mono-chlor (or mono-brow) hydroquinone. Adurol-Hauff has the formula Cl(OH and Adurol-Schering CB Br(OH)1 —their actions being similar. The developer as purchased is in the form of a white or greyish white crystalline powder, readily soluble in water and alkalis. In its action and results it resembles hydroquinone, but it is more soluble, keeps better, and the negatives are slightly softer. The addition of potassium bromide as a restrainer has not much effect, and the developing action is not much slower when the solution is cold. Since its introduction many formulae have been published for one-solution, two-solution, and three-solution developers. The following are those in most general use : Sodium sulphite . 8 oz. g.
Potass. carbonate . 6 „ Water . . . zo „ i,000 ccs.
Shake till dissolved, then add Adurol . . . I oz. roo g.
For negatives and gaslight paper dilute with 3 to 5 parts of water ; and for bromide prints with from 7 to io parts of water.
The above is a one-solution developer, and may be used over and over again. The formula for the two-solution developer is : No. i. Adurol . . 85 grs. 17 g.
Sodium sulphite . If oz. 175 „ Water to . . io „ 50o ccs.
No. 2. Potass. carbonate. If „ 125 g.
Water to . . io „ 50o ccs.
For use with plates and gaslight paper mix 3 parts of No. i with z parts of No. z ; for bromide prints add an equal quantity of water.
A three-solution adurol developer is as follows :— No. 1. Sodium sulphite . 65o grs. 13o g.
Adurol . . 8o „ 16 „ Water to . . pp oz. 50o ccs.
No. 2. Sodium carbonate. 'coo grs. 20 g.
Water to r oz. 5o ccs.
No. 3. Potass. bromide . 48 grs. io g.
Water to . . r oz. 5o ccs.
For soft negatives mix r oz. of No. i, 310 minims of No. 2, and 20 minims of No. 3. POT more brilliant negatives use io drms. of No. 1, f oz. of No. 2, and + drm. of No. 3. The three-solution formula is best for time-exposed plates, and when over-exposure is suspected.
Adurol combines well with metol and gives a developer which acts like metol-hydroquinone. One formula is :— Metol . . . r3o grs. 13 g.
Adurol . . . r oz. ,, Water to . . . zo „ i,000 ccs.
Dissolve and add gradually— Sodium sulphite . 7 oz. 35o g.
Potass. carbonate . 4+ 225 „ For negatives and gaslight papers, dilute with io times the quantity of water ; for bromide prints, with 15 times the quantity of water, or take of the stock adurol-metol developer as above r drm. and sufficient water to make z oz., and add a little bromide.
Adurol is the best developer for obtaining warm tones on bromide paper by direct develop ment. The concentrated one-solution developer as given above (let it be called A) is used with three others—namely, io per cent. solutions of potassium bromide, B ; ammonium bromide, C ; and ammonium carbonate, D. The colours are obtained by altering the exposures and vary ing the proportions of the four solutions.