The Dictionary Of Photography

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

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Efflorescence
Eikonogen
focus of parallel rays, r; p the lens;*and the diameter, cd, in fig. 46 is equal to ab, the diaphragm aperture, but in fig. 47 cd is greater than a b. Directions for finding the correct working aperture are given under Diaphragm.
Efflorescence. The giving up of water of crystallisation to the air, whereby a salt falls to powder. The behaviour of crystals of washing soda (crystallised sodium carbonate) in the air, is an example.
Effluviography. A name applied by Tomassi (in 1886) to the production of images on a sensitive plate by radiations from the silent electric discharge. It was almost an anticipation of what is now understood by Radiography (q.v.). The term Effluviography is sometimes applied to what is commonly termed Vapography (see Vapography).
Eikonogen, introduced by Dr. Andresen of Berlin in 1889, is the sodium salt of amido-/3-naphthol-/3-sulphonic acid, and has the formula C,0Hl5SO3NaOHNH2. It was first discovered by Professor Meldola in 1881.
Developer No. 1.
For Portraits and Landscapes.
Solution A.
Sodium sulphite ............ 4 parts.
Distilled water ............ 60 ..
To this solution add
Eikonogen ... ... ... ... ... 1 part,
which has been previously finely powdered by means of a mortar, and dissolve by shaking. Should a mortar be wanting, the solution can also be prepared by placing the salts into boiling
water, and shaking till dissolved.
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Solution B.
Washing soda          ............ 3 parts.
Distilled water         ... ... ... ... 20 ..
immediately before developing mix the developer as follows: -
Solution A ... ... ... ... ... 3 parts.
Solution B............... 1 part.
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