EIKONOGEN (Pr., Iconogene ; Ger., Eikonogen) A developer introduced by Dr. M. Andresen in 1889 ; it appears in a yellowish white powder or yellowish crystals when fresh, but rapidly changes to a brownish tinge. Its formula is (OH) ONa. It is sparingly soluble in water, but readily so in the presence of alkalis, especially when heated. It can be used in a one-solution or a two-solution form, and is suitable for all kinds of plates and bromide and gaslight papers. It is widely advocated for very rapid exposures, for which the following one-solution mixture, which is ready for use, is particularly suitable : Eikonogen . . . roo grs. zo g.
Sodium sulphite . . 200 „ 11 Sodium carbonate . roo „ 20 „ Potassium bromide . 5 „ I 17 Water . . . ro oz. r,000 ccs.
The small quantity of bromide added appears to increase the density of the negative, but where there is a suspicion of under-exposure and when soft portrait negatives are desired, it is better omitted. Bromide acts very powerfully with
eikonogen, and further additions in cases of over-exposure should be made cautiously. The following is the formula for the two-solution form : A. Eikonogen • . r oz. 50 g.
Sodium sulphite • 4 A 200 „ Water . . . zo „ 1,00o ccs.
B. Sodium carbonate 3 „ 15o g.
Water . . . zo „ r,000 ccs.
For use, mix r part of A, r part of B, and 2 parts of water. Potassium carbonate may be used in place of the sodium in the B solution, and a more energetic developer obtained. When eikonogen is used for wet plates they generally need to be intensified, preferably with pyro silver. (For an eikonogen-hydroquinone com bination, see " Developers, Mixed.")