. The book of photography; practical, theoretical and applied. these are employed, then the propor-tions used should be in exact ratio to theirchemical equivalents. This is estimatedby finding the proportion the weight ofchlorine it contains bears to the full mole-cular weight. Sodium chloride, we haveseen, is 585, potassium chloride is KCl, or39 + 35 5 74-5Barium chloride is BaClo -I- 2HoO, or in the first case, out of 585, 355 ischlorine, whilst in the last only 71 partsout of 244. So that 244 parts of the latterwill be required to equal 117 parts of theformer. On the whole
. The book of photography; practical, theoretical and applied. these are employed, then the propor-tions used should be in exact ratio to theirchemical equivalents. This is estimatedby finding the proportion the weight ofchlorine it contains bears to the full mole-cular weight. Sodium chloride, we haveseen, is 585, potassium chloride is KCl, or39 + 35 5 74-5Barium chloride is BaClo -I- 2HoO, or in the first case, out of 585, 355 ischlorine, whilst in the last only 71 partsout of 244. So that 244 parts of the latterwill be required to equal 117 parts of theformer. On the whole, however, chlorideof ammonium is to be preferred. The same 168 THE BOOK OF PHOTOGRAPHY. pi-ecaution as to purity must be taken as solution is sufficient to coat two sheetsin the pLiin salted process. of paper 22 in. by 17J in. Mixing the Albumen and Chloride. In order to mix the chloride properly,it essential that the fibrous nature ofthe albumen should be dsstroyed ; there-fore another violent beating with, theegg-whisk is necessary, until the albumen. Papek to be Used. A perfectly pure paper is not quiteso essential as in the process previouslydescribed, the chief consideration beingthat it is of a good colour and sufficientlyopaque ; that is to say, when laid overa sheet of newspaper, the reading mattermust not show through. Provided thepaper fulfils these conditions, its thick-ness is of no consequence. Suitablepapers may be obtained in small quan-tities from the dealers—the usual size is22 in. bv 17A in. ; but if the size referred to
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectphotography, bookyear
