The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186800009
• PURL: http://digital.slub-dresden.de/id1780948042-18680000
• OAI: oai:de:slub-dresden:db:id-1780948042-18680000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

344 THE PHOTOGRAPHIC NEWS. LJULY 17, 1868. ether. We have detected the presence of formic ether in the liquid, the boiling point of which ranges between 509 and 100° Cent.; by boiling with potasli and distilling with sulphuric acid a strongly acid liquid was obtained, present ing all the characteristic properties of dilute formic acid, and capable of reducing nitrate of silver and mercurial salts. We believe, therefore, that the reaction of bromine upon the ether of Kay is correctly represented in the equations :— 1. CH (OC 2 H5)3 + Br 2 = CO (OC 2 HS)2 + Br C 2 IP + H Br. 2. CH (OC 2 H53+ H Br = CHO (OC 2 H 5 ) + Br C 2 IP + C 2 H« 0. These equations we have verified by taking account of the ether and bromine employed, and likewise the bromide of ethyle and carbonic ether obtained. The first reaction consists, therefore, in the liberation of an ethyle and one of hydrogen of the tribasic formic acid by the bromine; the carbon of the radical of which one aftinity has been liberated combines withan atomicity of an atom of oxygen liberated by the removal of the alcoholic radical. If the reaction is regardad in this light it is pos sible to realise the inverse reactions of the nascent hydrogen upon bodies containing carbon, connected by two affinities with one atom of oxygen. Orthocarbonic acid is attacked by bromine in a cold state, giving rise to bromide of ethyle and carbonic ether; upon the latter, bromine reacts only when warm, disengaging carbonic acid and leaving bromide of ethyle. In both cases other bodies are likewise formed, but the nature of these we have not as yet studied. Acetic ether, when cold, is not attacked by bromine, but on warming the mixture in sealed tubes products of substi tution are formed, and bromide of ethyle. Oxalic and ben zoic ethers are not acted upon by bromine, even when warm’; while, on the contrary, ethylglycolic acid yields bromide of ethyle when heated with bromine. We propose making a deeper study of the reactions herein mentioned, and will give shortly the results of our researches. AN EASY MODE OF OBTAINING THE POSITION AND FOCUS FOK FIELD VIEWS. BY W. CAMPBELL* Many years ago, perhaps a dozen, I was very enthusiastic in my profession ; indeed I am so still, though it may be there is not that ardor displayed now which characterised my pur suits then. I loved and longed to carry from the field the pretty scene I looked upon, and to obtain it I often showed an enthusiasm which, had it been exhibited in a less laud able undertaking, would, I am sure, have seemed very un becoming. To ask a perfect stranger to allow me the use of his window, or to run into a man’s garden, to obtain a better view without once saying, 1 If you please, sir!’ were among the least of my impertinences. When I look back upon them I fairly blush ; but what will enthusiasm not do ? It clouds the vision, dims the light of more refined sentiments, and, if not mean, is certainly selfish. I never dreamed of any wrong. However, I never met with a rebuff; on the con trary, I had many kind invitations, and I am now of opinion that the public are not only tolerant, but indulgent to the enthusiastic photographer. In my pursuits I often found much time was lost in ascertaining just the right distance required to obtain the field on the ground glass, especially if a house was in the view as a principal object; and also time was lost in the focussing. Now, could I have a sure mode of placing the camera without the trouble of using a black cloth, and have it in focus ready to proceed, I fancied 1 should be a gainer. So I set to work and overcame the difficulty. I proceeded thus: I soon found that all objects in the field of view were in the right focus beyond a certain distance; there was therefore no further necessity for focussing on the field ; all I had to do was to make a line, drawn on the base of the * Humplrey's Journal camera, and consider this as the focal point for field view. The next thing was to get the area of the field of view. To do this, I took a cardboard, and bending it in the shape of a funnel, I looked through the large end, and contracting the smaller, so that it would circumscribe the same area ar the lens would circumscribe on the ground glass, I fixed it there. This 1 kept as a guide, always in my pocket, so that when I wanted to know if a particular spot would be in the field of any view I wii hed to take, I had only to apply to my cardboard funnel for the information. Exercise, how ever, toon gave me experience, and I could tell with my bent hand, looking through the opening made by closing the fingers over the thumb, what to expect. I had still another trouble. The point selected as the centre of the view could not be placed on the centre of the ground glass without looking. It was either too high or too low, too much on the left or too much on the right; of course it in volved the necessity of shifting the camera with black cloth over my head; this was troublesome, and had to be reme died. After some time I hit upon a plan. I remembered that in fixing a gun it must be so placed that the sight cover's the object, so I followed up this idea. I drew a line on the top of the camera corresponding with an imaginary line drawn through the centre of the lens to the centre of the ground glass; and in front, on the top of the camera, I made a small hole, and on the back made another hole; on the line in each of these two holes I placed a peg of wood, and they sighted my object, and was pleased to find that I was right. The ground glass showed on the centre, the object 1 had sighted on the top of the camera. The whole affair was now brought to a nicety. When I wished to get a view, I first applied my cardboard funnel; to get the area and distance, of course, if too large a field of view was seen, I had to go forward ; if too small, I had to retire from the object. Having got the distance, I then set up the camera, and drew it out to the marked line for the focus; then, looking over it, I brought the two points of sight to cover the centre point, and then proceeded to take the picture. I never looked to see that I was right; I was sure I could not go wrong. NEW KEO COLOURING MATTER. Dr. Adriani describes, in the Chemical yews, some experi ments with rosolic acid, or aurine cake, in the production of various forms of a colouring matter yielding many brilliant tints of red. The tinctorial power is stated to be very great, and although the red rosolic acid has generally been regarded as fugitive, the new combinations seem to give promise of more permanency. Amongst other experiments, he says :—“ I tried a solution of aurine in carbonate of ammonia, and precipitated it with chloride of barium ; after repeating the process already described again, I obtained in this way a very brilliant flesh- coloured pigment. I mixed, in an earthenware glazed mortar, some aurine cake and strong baryta water, Altered this mixture, and added to the flitrate very weak sulphuric acid, just enough to neutralize the baryta; in this way I obtained a pigment which, after drying (of course some washing, but not to excess), can vie, in beauty and tone of colour, with genuine carmine. I next proceeded to precipitate an aqueous solution of sulphate of zinc with a very slight excess of a solution of aurine in dilute caustic potassa, washing again, slightly, the precipitate, and drying it at 212°; the pigment so obtained has a fine rose colour. On trying sulphate of zinc again, but with a solution of aurine in dilute carbonate of potassa, after drying, a very peculiar and somewhat dull pinkish-coloured pigment is ob tained. A most magnificently bright scarlet, of deep hue, is obtained by first triturating together some previously sepa rately-powdered aurine with lime-water (not milk of lime), filtering the turbid liquid, and next passing gently through it a current of carbonic acid gas. A precipitate ensues exhibiting the colour already referred to ; on drying it, after having care fully collected it on a filter and slightly washed it, I find that I even below 212° its colour is very much altered and impaired. I find, however, on instituting experiments on purpose, that ii the pigments referred to are dried over sulphuric acid at the