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542 THE PHOTOGRAPHIC NEWS. [August 24, 1883. but, still faithful to the old love, thinks that equally good results may be obtained from stone, especially if two rollers are used for inking, one charged with ordinary printing ink for the body of the work, and the other a glue roller charged with a thinner and coloured ink, to complete and soften the first inking, and give a more agreeable appearance to the print. He even ventures to think that stone will be brought into use again, as offering more security in the daily practice of a large printing office. Whether this will come to pass or not, it is impossible to say ; but it is probable that the use of stone in collotype printing might be attended with advantage. The porous nature of the stone would enable the gelatine film to be held more firmly than it can be on glass or metal, and also, by its capacity for retaining moisture, the stone would afford superior facilities for keeping the gelatine film in a proper state of dampness without the necessity for constant spong ing. The weight of large stones and the difficulty of handling them in the dark-room must, however, always act as a bar to tbeir extended employment for photographic work. (To be continued.) SOLID AND LIQUID ILLUMINATING AGENTS. BY LEOPOLD FIELD, F.C.S.* Wax next demands our consideration. Here I must call your attention for a moment to the manner in which I have divided the various substances that subscribe to the definition of fats. This is quite arbitrary on my part, and I am emboldened by the fact that evory authority on the subject has followed his own ideas, and given his own definitions. Fats proper, I think, are such bodies as yield glycerine upon saponification. According to this definition, very few of the bodies we shall have to discuss can be called fats. But I have given the word a broader signifi cation, and propose to extend the name to embrace all substances which possess both lubricity and inflammability, and leave a more or less permanent transparent stain upon paper. By taking for the nonce, this view, we are enabled to include the paraffins, olefins, and waxes; also turpentine and camphor, with their isomeric essential oils. Oils themselves have long been divided into fixed and volatile, the latter being also termed essential. With these we have nothing to do ; they are all isomeric either with turpentine, as lemon, bergamot, orange, and many other well-known essences ; or with camphor, as rosemary, lavender, rue, and that class of perfumes. Turpentine and camphor may have to be mentioned in the lecture on lamps, but quite cn passant. The term wax used to be applied solely to beeswax, but of late years the introduction of paraffin, solid and liquid, has led to the name being employed to distinguish the first, paraffin proper, from the oil. So the white solid rejoiced in the desig nation, “ paraffin wax,” until the cognomen being dropped alto gether, we find certain companies advertising their goods simply as wax candles, a confusion of names which must be deprecated, as tending to mislead; perhaps, however, this is the end in view. Wax may be defined as bodies of a certain viscid plasticity when warmed, consisting of fatty acids of the series Cn H 2n 0 2 either free, or in combination with an alcohol radicle ; they do not yield glycerine upon saponification, which is effected with difficulty, and the soap formed is sparingly soluble in water. Following these lines, we have the following genuine waxes of interest to us :— Animal Vegetable We will take these seriatim. Beeswax is the gift of the ordin ary bee. It has long been an open question whether the wax was in the pollen of the flower, the bee acting as a mere vehicle, or whether the insect evolved the wax by some process best * Continued from page 525. (Bees-wax J Spermaceti [ Pih-la f Carnauba wax J Myrtle „ । Palm „ Origin. Apis. Physeter maero- eephalus. Coccus sinensis. Copernicia cerifera Myriea cerifera Ceroxylon andicola Jihus succedanea known to itself. When, on experiment, it was found bees who were fed entirely on sugar continued to produce wax, the ques tion was considered settled; namely, that the wax was as genuine a bee product as the silk of the worm. But later in vestigations show that, after two or three days’ sugar diet, the bees fail to supply any more wax, and ultimately die. Carefully considering all I have been able to find upon this subject, I am inclined to think that pollen is necessary for the formation of wax; in the first place, it nourishes the bee, containing nitrogen, which sugar does not; and secondly, itself containing wax, probably gives the initiatory to the wax-producing organs. It is a fact, that a colony of bees, deprived of pollen, will take eighteen ounces of honey to produce an ounce of wax ; whereas, with a proper supply of “bee bread,” only fifteen ounces of be consumed in making the same quantity. The wax exudes from between the lower rings on the abdomen of the bee, and is worked up between the fore-paws, for though of high melting point (145° F.), it becomes plastic at 90°, and can be readily moulded. The composition of beeswax has been fruitful subject of discussion amongst chemists, who have obtained results of startling discrepancy. This is, doubtless, due rather to the adulteration of the wax before analysis than variation in the substance itself, it being generally found that substances of animal origin are very uniform in composition. Mr. Otto Hehner has recently made a most exhaustive investigation of a great number of different waxes, and comes to the conclusion that the average composition is— Cerolein (?) Myricin ... ... ... ... .88 Cerotic acid 42 in 100 parts of wax. These two constituents may be easily separated by boiling the wax with alcohol, when the cerotic acid dissolves, leaving the myricin, which is a true typical wax, being a palmitate of myricyl CaHa | o, : it is finely crystalline. C3oBg ) Perhaps, if there be cerolein, it is that which, by its abundance or exactness, gives the characteristic qualities to all these different waxes. On this stand there are over forty varieties, from every country at all noted for that product, and yet an experienced eye and nose will pick you out and assign most of them to their native lands. Here we have bright yellow wax from Holstein and Denmark, the golden produce of Senegambia', the parti-coloured mixture from Australian hives, and the soft, dark ceral of Mogador. This gamboge-tinted specimen comes from Mexican woods; this is wasp-wax, soft and dirty-looking ; this again, almost white, comes from Brazil. According to Mr. Hehner, whatever the physical properties and appearance of these multichroic specimens, their composition varies but little. Even that little he inclines to attribute to man and the advance of civilisation, rather than to any fault on the part of the bee. Of old, if the sable bee-owner had not sufficient tale of wax, he artlessly introduced a stone or lump of iron, or a bone or two, to make up the weight, or, at most, stirred in a quantity of coarse sand. But now every con ceivable fat, cheap paraffin (imported for the purpose), palm oil dregs, &c., are employed as adulterants, not detected till the bleaching ground or candle, by defective performance, exposes the deception. There is no remedy. The agent who collects the tributary supplies from a hundred homesteads, mixes all the lots, and the hundred agents’ deliveries are again thrown together. What help is there? But, by careful sampling, a keen buyer manages to escape with about 75 per cent, of pure wax. This comes to the factory as you see it, and, in its present form is use less. The first step is to “clearit down”—which is much the same as “ rendering ”—boiling with a little weak acid and water which separates all dross, and leaves the wax clean, though dark in colour. The next operation is that of bleaching. This may be done in two ways—by air, or chemical action. The latter can only be applied to wax that is not intended for candles ; the grain becomes highly crystalline, and the burning power deteriorates. Why this is, I cannot say, as yet; we must look to Mr. Hehner’s researches for the future explanation. To whiten the wax chemically, it is treated with sulphuric acid aud bichromate of potash, whereby ozone is liberated, and that discharges the colour. As the chromium salts impart a powerful green tint to the wax, it has to be boiled considerably with further libations of acid water, till, finally, it assumes this appearance. Observe how short and friable the grain here—you will see the crystalline structure upon closer inspection. If 1 were authorised to hazard an explanation, it would be, that in the gentle performance of atmospheric bleach