A Manual Of Photography

75 THE CHROMATYPE. in ite manipulatory details, and produces very charming positive pictures by the first aPP^^ the above process of Mr. Pon- The chroma VP®^ practice that the bichromate of potash ton s, hut it was found p . effect - the following alone would not produce the desired enter. method was therefore adopter : absolved in an ounce of One drachm of sulphate of copp a saturated distilled water, to which is added halt an the solution of bichromate of pot^this elution ^PP be surface of the paper, and, when dry, it is ht lor ,, kept for any length of time without spoiling WV to sunshine, the first change is to a àll bro°u^^ if the in this stage of the process veg^andwe action of the light is contoured the1£ either have a positive yellow plot from the sunshine, is washed ease, if the pi»per, when ^re J ^ , very beautiful positive over with a solution ot nit found advantageous to picture results . In practice, -t °åt ; the picture allow the bleaching actio 8 g more defined than that resulting from this will be clever thc brown etage, which is procured when the àonnen the nitrate of To fix these pictures it is necess 5 ^er - if the water silver, which h^ttft suffers, and long soaking in contains an) muriates tne i f common salt are such water obliterates it, or if a few grains oi co added to the water the apparel, , necessary picture is, however capable 0 °à^ an hour, when it bemg to expose it to suns' ^^ur, it becomes lilac revives ; but insteau oi ociug mmnfitv of salt used the shades of colour depending upon ,> the shadow parts to decompose the chromate of silver which forms the snaa P of the picture. that if we substitute Mr. Bingham remarks on this process, th more sulphate of nickel for the su p a 6 ld^opedby nitrate of sensitive, and the picture is more clearly developed y silver. . § - ^ocess possesses some ad- The following -^X of copper we add a vantages. If to a soiuu potash, a very copious brown solution of the neutral 1 ^ Tomate of copper. If this precipitate falls, which ^sd, is added to water acidulated precipitate, after bel g dissolved, and a dichromatic solution is with sulphuric acid, i upon paper, is of a pure yellow. A formed, which, when Tipiers washed with this'solution is very short exposm-eal « I the äw from the paper, and quite sufficient to oisciiaiguj