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The photographic news
- Bandzählung
- 6.1862
- Erscheinungsdatum
- 1862
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
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- Public Domain Mark 1.0
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- urn:nbn:de:bsz:14-db-id1780948042-186200003
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- http://digital.slub-dresden.de/id1780948042-18620000
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- oai:de:slub-dresden:db:id-1780948042-18620000
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- Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
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- Parlamentsperiode
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- Wahlperiode
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- Bandzählung
- No. 200, Juny 4, 1862
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
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- Wahlperiode
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Zeitschrift
The photographic news
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Band
Band 6.1862
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- Ausgabe Ausgabe 73
- Ausgabe Ausgabe 85
- Ausgabe Ausgabe 97
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- Ausgabe Ausgabe 589
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- Ausgabe Ausgabe 613
- Register Index 619
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Band
Band 6.1862
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July [July 4,1862. THE PHOTOGRAPHIC NEWS. 318 Am arrive, order AH 1 of its pot preparin, forest. I with car to evapr of trans The salt of base t analogoil crystals 1 dissolvin io alcoh one part nentralis and then the solut sited in and has tquivale piven of liquid, ■ dialed i klt, whi 'lightly Wing. Pormi •re likel Portance foe the c 8 formei Mash,: Mt cut Gnstic t Wiques Sven mo by disso tv aporai potash of commerce is obtained. Bi-tartrate of potash is th 11 salt commonly known as cream of tartar. The crude tart or argol is partially purified by solution, filtration, apl crystallization. The lime is then separated from itbytredl ment with dilute hydrochloric acid and washing. Te salt then forms a white hard crystalline powder, having 2 slightly acid taste, and being permanent in the air. It 2 very slightly soluble in water, and is of no especial interest, except as a means of forming the Neutral tartrate of potash.—This is formed by treating the bi-tartrate with water and carbonate of potash, unt the acid reaction is neutralised. By slow evaporation the salt is obtained in transparent colourless prisims. Thesf fuble in water. 80UT sxhibite ‘graph Agesh Moure t "e und Contribi Sk Sdvig deligat el pa s co: 'noil,, feed thefles 0il col Bomeo tiyes, s the att in cult QLevei the ori PHOTOGRAPHIC CHEMICALS: TMEI Manufacture, Adulterations, and Analysis. Potassium Salts (continued).—Acetate of potash, and the corresponding soda compound, are of frequent use in the laboratory, photographic as well as chemical, to re place a strong acid such as nitric, sulphuric or hydro chloric by a weak organic acid. For instance, free nitric acid in the silver bath, the presence of which gives rise to well-known objectionable qualities may be replaced by acetic acid by the simple addition of one of these salts. We may as well briefly point out the rationale of this replacement. When a certain amount of acetate of potash is brought into contact with a liquid containing free nitric (or other mineral) acid, a decomposition takes place. The potash finds itself in the company of two acids which have a strong but unequal liking for it; and the attraction being reciprocated in the same degree, thepotash combines with the acid for which it has the greater affinity. Nitric acid and potash having a far greater affinity one for the other than acetic acid and potash, unite and form a solution of nitrate of potash, leaving free acetic acid instead of free nitric acid in the liquid. Of late years the exact and sharp decomposition here described has been doubted by some writers, who consider that the solution, under the above circumstances, would contain a mixture of nitrate of potash, acetate of potash, nitric acid, and acetic acid. Whether this theory be correct or not, it would be very difficult, if not impossible, to say, but it is sufficient for our purpose to know that a liquid treated as above acts as if there "e" ( only free acetic acid present. ‘ ...1 Acetate of potash may be readily prepared by neutralisin I carbonate of potash with acetic acid and evaporating. 1 ! the acetic acid and carbonate of potash are pure, the result' I ing acetate will be ready for use at once; as, however, th former generally contains traces of empyreumatic matter this will have to be removed from the acetate in the follon ing manner :—evaporate the mixture with continual add. ! tion of acetic acid, so that the potash may never be in exoeS from evaporation of the acid, as that would cause decomposi tion and introduce fuither impurities. The concentrated liquid is mixed with one-tenth of its weight of animal char coal, then evaporated to dryness, and the mass heated unti it fuses; the fused mass is then dissolved in water and tho liquid filtered; a little carbonate of potash that may hare been reproduced by the fusion is then neutralized with 11 strong acetic acid, and the solution is to be evaporated to • syrup and allowed to crystallize. It may also be prepar™ I by double decomposition between acetate of lead and sub I phate, or carbonate of potash. We do not, however, re commend this, as the process in inexperienced hands, liable to give an impure product. Acetate of potash in the dry state melts below a red heat, forming an oily liquid, which on cooling solidifies to a white, opaque, crystalline mass. The aqueous solution, when evaporated to dryne I with constant stirring, becomes covered with a white crust of anhydrous salt, until the whole liquid is converted in® a dry powder. If the evaporation be stopped as soon as the crust begins to form, and the liquid then allowed to cool large transparent prismatic crystals are formed which con tain water of crystallization. The salt has a warm and I pungent saline taste. When the anhydrous salt is heated above its fusing point it is decomposed, yielding acetic acid, and several other liquid and gaseous products, having * residue of carbonate of potash and charcoal. Acetate of potash deliquesces very rapidly- in the air, and dissolves at the ordinary temperature in less than one-fourth of is weight of water. When it is dissolved in a considerable quantity of water, and allowed to remain for some time ( a . s in the test bottles on the laboratory shelves), a decomposi tion takes place, carbonate of potash is formed, with pro duction of fungi. Acetate of potash when dissolved to saturation in boiling water forms an oily liquid, boiling a ' 169° C., containing one part, by weight, of water to eigb f parts of salt. Acetate of potash also dissolves very readil in alcohol, requiring only three parts of the cold or t") parts of hot liquid, from this solution carbonic acid pref pitates carbonate of potash. Tartrate of potash.—Before describing the neutral tartrot" we think it will be more convenient if we give a short accob of the acid compounds, as it is from this that most of tb fortunately, have been slightly touched in body colour, and show the action of the damp walls. The whole-plate por traits of Maull and Polyblank are in many respects good, and altogether much better than their card pictures. Mr. Charles Newcombe contributes some pleasing pictures. Ross and Thompson’s portraits have many artistic qualities. Heath and Beau exhibit some characteristic heads. Mr. McAndrew has some fine bold round vigorous heads. McLean and Melhuish have some specimens, many of which display very excellent qualities. Touched portraiture is, we are happy to say, only con tributed by very few persons. Why it is contributed at all, or why admitted at all, after the announcement to the contrary, we cannot understand, unless it be that unscrupulous persons sent in such pictures to fill the space granted to them, and it was thought better to wink at the broken condition than leave bare walls. Certain it is that some are there. Mr. King, of Bath, sends a large number of these spoiled photo graphs very gaudily done, and some of which are showing yellow stains of decomposition already. Mr. Mayall sends some very carefully worked pictures in black and white, which are, to our taste, infinitely inferior to untouched prints from the same negatives, some of which we have now before us. Mr. Eastham, of Manchester, sends a large com position group, which is very good, but being touched has no business here. The same may be said of some positives by the tannin process upon enamel glass. The examples of solar camera enlargement are not nume rous in the British Department. M. Claudet contributes the largest number, and many of them are very fine indeed; but some of them are touched. Mr. Owen Angel, of Exeter, has sent some very good enlargements ; but apparently as con scientious in his regard to the conditions issued, as others have been unscrupulous, he has not even touched out slight accidental spots. Messrs. Smyth and Blanchard exhibit some very fine enlargements (609), which are to our taste the finest in the department. On the same screen, as if hung as a foil to that just named, is a picture about half life-size, by Cramb, Brothers, of Glasgow. This is minutely de scribed as being taken direct in the camera without enlarge ment. We can only regard it as having been sent as a specimen of what to avoid, as anything more hideous, clumsy, or inartistic we have rarely seen. are permanent in the air, but very sol Tartrate of potash is of interest, as it offers a ready means obtaining the corresponding silver salt by double dew 1 " position. Tartrate of silver has not yet been much e® ployed as a photographic agent, but it possesses mAi qualities which would render its further investigaton 1 this respect desirable. a , Citrate of potash.—The silver salt of this acid has bent used in photography with marked success, and on acco
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