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708 THE PHOTOGRAPHIC NEWS. LNOvEMBER 6, 1885. dress and loud curtain in most of them. One of the studies, however, a figure reclining on a divan, is really powerful and striking. F. H. Morton sends “ Snowdon ” (No. 336) and two others, of which No. 521, “ Fairies’ Glen,” shows a very curious effect in the sky and tree tops that looks like a combination of halation and reversal of image. J. Bowen’s “Portraits” (No. 337) are large heads, rather- wanting in detail and softness. His other frame (No. 647) shows better work. “ Marine Studies ” (No. 342), by A. Hamilton Clarke, is a set of flying shots, of which some would be improved by more careful vignetting. No. 344, “Lowestoft Pier,” by II. W. Beven, would be better if the sky had not been printed so dark. No. 668, “ The Burning Pier,” makes a striking picture of a kind that it does not often fall to the lot of a photographer to secure. “ On the Clyde ” (No. 345), by J. Hyslop, is a good set of five pictures of vessels. Of H. H. Stole Bailey’s five exhibits, we prefer “ Castle Hill, from the Harbour, Scarborough ” (No. 357). C. A. Ferneley has three small views (Nos. 361,362, and 363), of which 362, “ Low Tide,” shows a vessel with the fault of having the artificial sky outside the rigging, and the natural sky within it, disagreeing. Of this exhibitor’s other works (Nos. 522, 523, and 547) the last named is the best. James Crichton’s frame (No. 369) contsins a number of groups of fisherfolk—mostly taken on the shore—which show much power in inspiring the models with the ideas of the artist. The people appear to be engaged in their natural occupations, and unconscious of the camera. Oneof these groups, “The Washing Day,” is here reproduced. J. G. B. Wollaston’s “At Shoreham (No. 371) repre sents a pretty view of trees and a pathway. Another is a rural scene with water. No. 455 and 456 are from paper negatives. The former represents a group, and is harsh; the latter, a photograph of a bridge, is good. No. 411, 4 picture of a quiet church and churchyard, is pleasing and restful. Nos. 573 and 581 are pictures in which there is some nice foliage, not much improved by the figures that have been introduced. No. 583 is a pretty picture in cluding trees and a garden path. No. 614 is an interior, very dark at the lower part. Nos. 791 and 796 are paper negatives mounted between glass to be examined by transmitted light. We notice lines in some of these, as if the paper had been creased. PRACTICAL CHEMISTRY FOR PHOTOGRAPHERS BY RALPH W. ROBINSON. II.—Soda, and How to Test It. In this article it is proposed to treat of the quantitative estimation of the chloride of sodium in a sample of car bonate of soda, it being an important point that the alkali used to prepare a developer should not contain much of this s -It, as it acts as a restrainer. The apparatus required is the same as was used for estimating the actual carbonate of soda in our sample. The principle on which the estimation of a chloride depends is, that in neutral solutions containing a chloride and a chromate, a known quantity of nitrate of silver will first precipitate all the chlorine in the form of white, or whitish chloride of silver, and as soon as all the chloride is preci- pited, red chromate of silver. We require, then, a solution of nitrate of silver, a known volume of which will precipi tate a known quantity of chloride. The most convenient strength for our solution, we shall find, is that which con tains one grain equivalent (170 grs.) of nitrate of silver to 1 litre (1,000 e.c.) of water. Nitrate of silver is repre sented by the formula AgNO 3 , which means that it is com posed of 1 atom of silver, 1 atom of nitrogen, and 3 atoms of oxygen, and its equivalent weight is made up thus (Ag=108,N=14,0,=48)=170. Now, as it is desired to make 1 litre of standard solution, we weigh out 190 grs. of nitrate of silver and dissolve in 1,100 c.c. of distilled water, which will provide enough to leave sufficient solution to test the strength of what has been made, and will also be a little too strong, so that when we have estimated the actual amount of silver con tained in it, it can be diluted with water to the required strength. Having dissolved the nitrate of silver and mixed thoroughly, we weigh out 585 grs. of pure chloride of sodium, which has been thoroughly dried by heating in the porcelain crucible, and then powdered. Dissolve this in distilled water, and make up to 500 c.c., and mix thoroughly. Now measure out three portions of this solu tion (say 25 c c. each) into basins or small flasks, and make up to about four ounces with distilled water. Add to each about five drops of a saturated solution of pure yellow chromate of potash. Now one equivalent of nitrate of silver will precipitate the chlorine from exactly one equiva lent of chloride of sodium (58’5 grs.) in the form of chloride of silver, which is represented by the equation :— Nitrate of Chloride of Chloride of Nitrate of Silver. Sodium. Silver. Sodium. AgNO, + NaCe = AgCl + NaNOj We fill the burette with the solution of silver up to the top mark, and then run some carefully into the first bash' or flask containing chloride of sodium, with continual stirring. A precipitate is immediately produced, chiefly white chloride of silver, but, where the silver first come 3 in contact with the solution, slightly red. This red colour is formed by the precipitation of chromate of silver on the part of the liquid when the silver has precipitated all the chloride, but, as long as any chloride is left in the solu tion, the red chromate on stirring is re-decomposed. When the whole of the chloride has been precipitated, this red