e for
the purpose the reproductions are made.

The sensitizing solution is similar to that published by Mr. Endemann,
viz.:

Potassium bichromate 460 grams
Sodium chloride 460 grams
Ammonium vanadate 0.75 gram
Sulphuric acid 1 liter
Water 13 liters

THE PRIMULINE OR DIAZOTYPE PROCESS.

Primuline, discovered in 1887 by Mr. A. G. Green, an English chemist, is a
dye of a primrose color, possessing a great affinity for cotton fibers, to
which it is readily fixed by simply immersing the material for a few
moments in a hot solution of the dye. If the material so dyed be placed
in an acidified solution of nitrous oxide, the primuline is diazotized,
forming a derivative compound of a deeper color, which fades in the light,
and which in presence of amines and phenols gives rise to a variety of
dyes whose color depends on the reagent employed, while, when acted on by
light, the resulting compound is entirely deprived of this property. In
other words, the diazotized primuline acts as a mordant only when not
altered by the luminous action.

The chemical change light effects in the diazotized primuline is not well
known. It is pretty certain, however, that nitrogen is set free, for if
gelatine imbued with primuline be immersed in water after insulation,
nitrogen is set free and can be collected as usual in a tub filled with
water and inverted on the substance.

By itself diazotized primuline is slowly influenced by light, but quickly
acted on in presence of organic substances. It is more sensitive when
applied on cotton or paper than on wool, silk, linen, and such organic
compounds as gelatine, albumen, caseine, starch, etc. Its sensitiveness
is about one-tenth less with gelatine than with cotton.

The sensitiveness of diazotized primuline to light, when united to organic
substances and the different colors which can be obtained with the
unaltered compound, have given rise to an interesting printing method, the
invention of Messrs. A. G. Green, C. F. Cross, and E. J. Bevan, which
yields _positive impressions from positive cliches_. The manipulations of
the process are simple:

In a certain quantity of rain water, kept at nearly the boiling
temperature by an alcohol lamp placed under the vessel, dissolve per cent.
2 parts of commercial primuline, and in this immerse, by means of a glass
rod, some pieces of calico--free from dressing--turning them over several
times du