SCIENTIFIC SUMMARY. 
415 
Water 
. 35 lj ounces 
. 200 grains 
. 1,543 „ 
. 185 „ 
Solution of sesquichloride of iron, sp. g. 1*53 to 1*6 
Chloride of copper, crystallized .... 
Pure hydrocloride acid, concentrated . • 
The paper is now sensitive, and after being- exposed underj the negative 
requires development by immersion in the following solution: — 
Water 35£ ounces 
Sulphocyanide of potassium 120 to 180 grains 
Concentrated sulphuric acid 15 grains 
The solution employed for preparing- the paper . 150 to 300 grains 
After floating the print on this bath for three or four minutes, it is im- 
mersed therein and remains for from five to thirty minutes, according to 
the mode of toning intended to be adopted. Fresh solution may replace 
that absorbed by the paper, and the bath will be found to improve by use. 
When developed, the proof is thoroughly washed in pure water from fifteen 
minutes to one hour, the latter being always sufficient, and then may 
either be toned at once or dried and toned at any future time. Proofs 
thus obtained may be brought to almost any required colour, either by im- 
mersion in a solution of from 0 to 12 per cent, of red prussiate of potassa, 
or in the following : — 
Water 
Protosulphate of iron 
Perchloride of iron . 
Hydrochloric acid . 
200 to 300 cubic centimetres 
100 grammes 
40 „ 
80 „ 
In using this bath, the water in which the print is afterwards washed 
must be acidulated. Photographers who use large sheets of paper for 
printing life-size portraits and large landscape pictures will doubtless 
rejoice in the publication of a process so economical. 
Adulteration of Chloride of Gold . — A discussion has arisen in the photo- 
graphic journals on the subject of the adulterations so commonly made in 
chloride of gold, which, started by Mr. J. T. Taylor, sub-editor of the 
British Journal of Photography , has been continued by the editor of the 
Photographic News and promptly taken up by some correspondents in both 
these serials. The evidence advanced seems to show that before the photo- 
grapher can get his fifteen grains of gold half its value is generally 
demanded for profit, and that in each such quantity there is frequently not 
more than six and three-quarter grains of pure gold. The subject has 
been before referred to, and Mr. R. Reynolds even went so far as to call 
the attention of the British Pharmaceutical Conference to the common 
nature of this fraud. As it is very desirous that operators should know the 
exact strength of the solution they have in use, several tests have been sug- 
gested, one of the most reliable of which, if not wholly reliable, is suggested 
in the facts that the most common element of adulteration is the chloride 
of sodium, cadmium, or strontian, either of which is not soluble in alcohol, 
while chloride of gold is. Mr. Taylor however denies that alcohol forms 
a sufficiently reliable test, and as the test by analysis is a very delicate ope- 
ration, which has the further disadvantage of rendering the gold useless for 
