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August 7, 1891.] THE PHOTOGRAPHIC NEWS. 563 The following formula has frequently been used: Dis solve in 100 parts of boiling water 30 parts of metabisul phite of potassium, and hereupon 10 parts hydrochloric para-amidophenol. To this solution (which will keep) slowly add, whilst stirring, some concentrated caustic soda until the precipitated para-amidophenol has just been redissolved. For practical use, the solution of the para-amidophenolnatrium obtained has to be weakened by adding 5 to 50 parts water, according to whether a strong or weak developer be required. It may be seen from this recipe that only just as much caustic soda is wanted as is necessary for producing the sodium salt, which is important to know, since, certain kinds of dry plates will not stand any surplus quantity of caustic soda. If carbonates of alkalis are used it will be necessary to weaken the developer considerably, owing to the para amidophenol being difficult to dissolve. The formula, as recommended by A. and L. Lumiere, is, in my opinion, too concentrated. As a rule, I have successfully been working with a solution produced as follows: — Water 1000 parts Hydrochloric para-amidophenol... ... 5 ,, Sulphite of soda (crys.) ... ... ... 50 ,, Carbonate of potash ... ... ... 25 ,, This developer, it is true, works a little more slowly than that produced with caustic soda, but it has proved highly useful, especially for time exposures. Para-amidophenol is thus a substance fully equal to any of the developers now used, but I would certainly give the preference to eikonogen—which, owing to its constitution, stands nearest to para-amidophenol—on account of its general usefulness. ADDRESS BY THE PRESIDENT AT THE OPEN ING OF THE AMERICAN PHOTOGRAPHIC CONFERENCE. Possibly the best service I can render you is to speak con cerning the present and the future of this Conference. In the first place, do not expect that a special national organi sation such as this will bound into existence, rounded out and fully inflated like a rubber ball, in the first year of its beginning. Let us rather be content as we are, a small but earnest band of men and women, with the elements of health about us—stability and growth. In this way we can gradually grow up to the situation that we are creat ing for ourselves, and ready to meet each untried question that is offered for solution. We are now on trial as an experiment. You and I believe that there is a need for us, or we would not be here to-day ; but we must show to the great army of camerists that this need applies to them as well as to us. Let us enumerate a few of the benefits that will accrue to the amateur from such an association. No one will deny that the camera club is a necessity to the uncommercial photographer. One cannot contain within himself all knowledge, all experience, limit the sub ject as you may. We learn from one another, and if a man is right-hearted, he is anxious to impart what he knows. It is true that we have teachers in books, and one may learn from them, but one may learn far more quickly from mental contact with the living teacher. A potent teacher is the work of others. In it you find a standard to measure the merits or defects of your own work. In this way you acquire one of the most valuable traits that make up the mental equipment of the artist—• After thus proving that not only the compounds of the para-grovp, but also those of the ortho-grovp, exercise a powerful reducing influence on the latent photographic image, it was also of interest to study the processes of oxydation the various substances on their employment as “developers” are undergoing, and especially to get acquainted with the fowl products of oxydation. As to the para-compounds, they have been known for a long time, when oxydised, to get easily converted into chinon, CHO, or chinon-like substances. That oxydation, on developing, actually takes place as above described I feel bound to conclude, because para-amidophenetol, C II NH, -sHOC,H, as I have proved, does not develop the latent photographic image. Nevertheless, the process is not a very simple one. The presence of chinon could not be proved in a hydrochinon developer exhausted through frequent usage. The oxydation of these compounds by means of bromide of silver in an alkaline solution appa rently leads to different final products. I am now engaged with the investigation of these processes. The capacity of the aforesaid ortho-compounds of benzole to develop the latent photographic image will have to be attributed to their being able, as lately shown by Lincke and Kiisterf to form chinon-like substances, as has been known for some time with regard to certain ortho derivatives of naphthaline, and is characteristically shown to be the case with eikonogen, As regards para-amidophenol, CeH, NII OH in particular, it should be premised that this compound is rather easily soluble in hot water, but comparatively difficult to dissolve in cold water. The para-amidophenol forms two groups of salts. With the aid of acid, salts may be got which mostly are easily soluble in water, and which, like hydro chloric para-amidophenol, CgH, 5NH,HCl ( O’ll ’ are dis ¬ tinguished by their great capacity to crystallise. From concentrated solutions of these salts, by an addition of carbonates of alkalis, the free para-amidophenol is pre cipitated. If still more diluted (f. i. 1:200), it will, however, remain undissolved even at the mean tempera ture of a room. By means of caustic alkalis, salts are produced in which the hydrogen of the hydroxyl-group is replaced by metallic alkali, as, for instance, para-amidophenolnatrium. Cg H{ NH, ONa These salts are easily soluble even in cold water. It follows that with the aid of para-amidophenol, two sets of developers may be produced, viz., those with carbonates of alkalis, containing the para-amidophenol proper in a dissolved state, and those with caustic alkalis, where an alkalic salt of para-amidophenol renders them effective. Both kinds may be said to be very useful. Para-amidophenolnatrium develops very quickly and powerfully indeed, the better sorts of dry plates in the trade, even without an addition of bromide of potassium, yielding absolutely clear and bright negatives, and showing the blue-black tint known as favourable for copying, which latter may also be obtained with hydrychinone. Reports of the German Chemical Society, xxi., 2719.