ANOTHER PROCESS—THE CYANOTYPE.
Float the paper on a solution of the sesqui-chloride of iron. Dry and expose, afterwards wash the prints, and then immerse them in a bath of ferrid cyanide of potash. The picture will appear of a blue color in all those places where the sun has acted. p210
PROCESS WITH SALTS OF URANIUM.
The paper, without having undergone any preceding preparation, except that of having been excluded from the light for several days, is floated on a bath of the nitrate of uranium as follows:
| Nitrate of uranium | 2 drachms. |
| Distilled water | 10 drachms. |
The paper is left on the bath for four or five minutes, it is then removed, hung up and dried in the dark room. So prepared, it can be kept for a considerable time.
The exposure beneath a negative varies from one minute to several minutes in the rays of the sun, and from a quarter of an hour to an hour in diffused light. The image which is thus produced is not very distinct, but comes out in strong contrast when developed as follows:
NITRATE OF SILVER DEVELOPER.
| Distilled or rain water | 2 drachms. |
| Nitrate of silver | 7 grains. |
| Acetic acid | a mere trace. |
The development is very rapid in this solution. In about half a minute it is complete. As soon as the picture appears in perfect contrast, the print is taken out and fixed by immersion in water, in which it is thoroughly washed.