NATURAL PHILOSOPHY. 143 



ANILINE PROCESS OF PHOTOGRAPHIC PRINTING. 



Mr. W. Willis of Birmingham has recently laid before the 

 Photographic Society an account of his aniline process of photo- 

 graphic printing. It consists of a new method of developing the 

 pictm'es produced by Hunt's chromatype process, in which the 

 paper is prepared with a solution of bichromate of potash and 

 sulphate of copper. The difficulty of finding a suitable develoijcr 

 for the prints so obtained has hitherto prevented the use of this 

 method. The em^jloyment of nitrate of silver or mercury, besides 

 being attended with some jiractical inconveniences, i^roduces pic- 

 tures of a red color, which, although suitable for the reproduc- 

 tion of the red chalk sketches of the old masters, is inadmissible 

 for ordinary drawings. According to Mr. Willis's process, the 

 paper is sensitized with a solution of bichromate of potash or 

 ammonia, containing a small quantity of sulj^huric or phosphoiic 

 acid, and, when dry, is exposed to light under a positive photo- 

 graph or drawing. It is then placed over a solution of aniline in 

 benzole, turpentine, or ether, preferably the former. The parts 

 forming the picture — i. e., those not acted ujion by the light — 

 arc developed of a mauve color, which is very permanent, not 

 being changed in tint by the application of acids or alkalies. The 

 process has already been introduced in Birmingham for the mul- 

 tiplication of engineers' drawings, in cases where the number 

 required is not sufficiently great to admit of lithography being 

 used with advantage. The property i^ossessed by bichromate of 

 potash of forming a black compound with a solution of logwood, 

 which has been used for the manufacture of cheap writing-ink, 

 has also been aj^plied by Mr. Fox of Edinburgh to the develop- 

 ment of these chromatype pictures. Both these processes have 

 been secured by patent. 



A new solvent for the greater part of the aniline colors has been 

 discovered by M. G. de Claubry, and communicated by him in a 

 pajier to the French Academy of Sciences. In jjlace of alcohol 

 and methylated spirit, which are high-priced or injui'ious to the 

 workmen, M. de Claubry proposes to substitute a decoction of 

 Panama bark {Quillaria), or of Egyptian soap- wort (Gypsophila) . 

 Solutions of the coloi'ing products can be easily obtained by pour- 

 ing the boiling decoction upon the powder-, after stirring and 

 decanting the solution, the operation must be repeated, if any 

 part of the powder remain undissolved. It was found that the 

 red colors dissolved most readily, and the blues less so. If, there- 

 fore, the coloring matter be purple, it is necessary at the end to 

 mix the different solutions together in order to obtain a dye of 

 the right tint. 



IMPROVEMENTS IN PHOTOGRAPHY. 



Photosciilpfure. — A process is now in use in London liy which 

 busts, statuette likenesses, etc., may be produced in clay or plas- 

 ter at a small cost, by the aid of photography. The operation is 

 as follows : Eight photographs are taken of "the sitter from eight 



