The Dictionary Of Photography

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

Home | About | Photography | Contact






Alcalinity                                                           Alcohol
albumen, gradually lowering the ends till it rests on the albumen. When the paper has floated for a few seconds, bubbles will be shown by the numerous puckers; lift the paper, and wet the bubbles with a camel's-hair brush; allow the paper to float for eighty seconds - not longer, or the albumen will sink into the body of paper - then gradually raise by one corner, and suspend from two corners to dry; when thoroughly dry, roll between steel rollers, and keep flat. Double albumenised paper is made by coagulating the first layer of albumen by floating on a mixture of two volumes alcohol and one volume of water. The paper is now dried and again floated on the salted albumen. The albumenised paper is sensitised by floating it, face downwards, on a solution of silver nitrate containing about 60 grs. to the ounce, three or four minutes being sufficient. Very full instruc-tions as to printing on albumenised paper are contained in some of the older books. We may mention " The Art and Practice of Silver Printing," by Abney & Robinson, London, 1888. (See Printing, and also Fuming.)
Alcalinity. The reverse of acidity, which see. (Also see Alkali.)
Alcohol (Ger., Weingeist, Alkohol; Fr., Alcool; Ital., Alcool), C2H5HO = 46. A generic term ; but when used without qualifica-tion common or ethylic alcohol is understood. Synonyms: Rectified Spirit, Ethylic Alcohol, Hydrate of Ethyl, Spirits of Wine. It is prepared by distillation from fermented saccharine solutions, or any vinous fluid. There are certain recognised strengths : -
Absolute Alcohol, which, as sold, may perhaps contain 1 or 2 per cent, of water. Specific gravity, -8oo.
Rectified Spirit. Old standard. Contains 16 per cent, of water, and is what is termed 56 degs. over-proof. Specific gravity, -838. New P.B. standard contains 10 per cent, of water, is 58 degs. over-proof. Specific gravity, .834.
Proof Spirit. Made by diluting five parts of rectified spirit with three of water.
The strength of alcohol can be very rapidly and accurately determined, provided nothing else but water is present, by taking the specific gravity and referring to a table such as is given under the heading Hydrometers and Hydrometry.