342 
POPULAR SCIENCE REVIEW. 
If then stirred, and allowed to stand for an hour or so the black sulphide 
of silver will be produced, and oxalate of ammonium contained in the 
liquid. The latter is then filtered off into a test tube and boiled with the 
addition of a drop or two of dilute acetic acid, and solution of sulphate of 
lime added when the production of a white precipitate insoluble in acetic 
but easily dissolved in nitric acid. This at once indicates the presence of 
oxalic acid. The writer then gives as the best remedy with which he is 
acquainted, the adding of a drop or two of solution of nitrate of lime to the 
bath, when the precipitate can be removed by filtration. Any slight excess 
of the nitrate of lime will not injure the bath. 
The Bromized Collodion Process. — This process of Major Bussells is de- 
scribed by the : editor of Photographic Notes , as 11 the first in point of 
absolute merit ” of all the “ dry collodion processes ; ” and he continues, 
“Nothing can surpass the beauty of its specimens produced by the Major 
himself. We have never seen foliage in all its depths so admirably rendered 
as in some of these specimens ; ” and moreover adds, that they are “the most 
sensitive plates ever exposed in a camera up to the present time.” Knowing 
these to be the opinions of a good practical and scientific photographer 
we give our readers the process, which is briefly this : — “ The collodion 
contains about 8 grns. of bromide of cadmium to the oz. and no iodide. 
The plates are immersed for ten minutes to a quarter of an hour in a 70 
grn. nitrate bath, acidified with nitric acid, and they are then washed 
excessively .” This is a point of primary importance. The washed plate is 
then coated with tannin, or some other suitable organic matter, and is 
allowed to dry spontaneously. The exposure is the same as in the wet 
process, and the development is effected by means of a solution of pyrogallic 
acid, to which carbonate of ammonia is added. No subsequent intensifica- 
tion is necessary, because any degree of density can be obtained by increasing 
the proportion of carbonate of ammonia added to the solution. To retard 
the action of the developer, which .would otherwise be too energetic, add 
bromide of cadmium, which must be very nicely proportioned to the 
quantity of alkali, a slight excess tending to enfeeble the image and too 
little to produce fog. The exact balance can only be hit by frequent experi- 
ment, and when attained, care should be taken always to preserve it. With 
this additional care the process is one of exceeding value both as regards 
the artistic value of its result and scientific accuracy of principle. We must 
add that the plates do not keep so long after exposure as others do. 
The Photographic Society. — The Photographic Times commenting on 
the present unpromising position and gloomy prospects of the London 
Photographic Society says, “ Only fancy an association having less than 300 
members, and an income of as many pounds (if every member pays), paying 
its secretary JloO per annum. This sum will seem the more inordinate 
when it is considered that the society holds but eight meetings per annum, 
and when it is considered that many competent men would be glad to hold 
the post as an honorary, appointed for the mere love of an art which they 
practise a3 a scientific recreation. 
Photography in London. — The offlcial catalogue of the Paris Exhibition, 
British department, gives the following statistical account of the number of 
persons engaged in photographic trade in London, exclusively of workmen. 
