THE CAMERA COLUMN.

New Zealand Mail, Issue 1404, 26 January 1899, Page 9

THE CAMERA COLUMN.

LiRTtiH ILIUaiMSTS

ADVANTAGES OF ACETYLENE GAB. The matter of illumination is a continual source of vexation to the amateur photographer who has a fancy for exhibiting his work in the form ox lantern suaes and who, while possessing a lantern of good quality, is forced by tho want of facilities for obtaining'oxygen and hydrogen (coal gas) when required to adopt the unsatisfactory substitute of a kerosene lamp. Kerosene has many objectionable features, apart from its inefficiency, and not the least of them is the tendency to “ creep ” and make the work of attending to the lantern dirty and unpleasant. In acetylene gas we have, a substitute for the oxy-hydrogen limelight which, while not perhaps so effective, is still far in advance of any form of oil burner. The gas, is easily made and used, and is apparently quite safe when rationally handled. It gives an intensely brilliant white light, and altogether promises to be “ a boon and a blessing” to the lantern owner. From an article on tho subject, in “ Photography ” we extract the following notes: — Acetylene has many advantages; it is true it has an unpleasant smell, as has also coal gas, but there is no need that

any should be allowed to escape, and whilst in illuminating power it is, of course, inferior to the limelight, it is far in advance of any oil lamp with which the writer is acquainted. A good generator must be used. There are so many now on the market that it would be unfair for any one who has not tried them all to make a selection as to which is best, but one or two characteristics that should be insisted on may be mentioned : (1) The cooling must be efficient. Acetylene is a gas in the formation of which heat is absorbed; it is, therefore, somewhat unstable. It is no doubt stable enough at ordinary temperatures, but it is possible that at high temperatures it might decompose with explosive violence. This is' certainly the case when tho gas is under great pressure, but it has not been proved to take place at tho moderate temperatures of an ordinary lantern generator; still it is well to be on the safe side. In one case which came upder the writer’s notice the carbide cylinder, when removed from the generator, was visibly red hot, and though no explosion happened, he would hesitate to work with a generator in which this was possible. (2) The gas receiver should be of considerable side, so as to bold a fair quantity of gas, and at the outset it must be full of water, not of air, otherwise the gas which first passes the jets will not light, but at the same time will carry enough acetylene through to produce a most unpleasant odour, and it may be some minutes—one case it took ten—before a steady flame is obtained, and all the time the hissing is very objectionable. (3) The receiver should be separate from the generator proper, so that the latter can be removed and recharged while the lantern is in use, and with but little escape of gas. This is very important. No one can judge exactly how long an entertainment will last, there may be unexpected delays, and it is most annoying to find the gas exhausted just when the last few pictures are to be shown. Generators having all these qualities are now to be obtained, and some at least have little to be desired. A great deal has been said and written about the dangers of impure carbide These are, however, entirely imaginary, as none of the impurities likely to be present can have any effect in making the gas dangerous to use. If calcium phosphide were present, which it never is, phosphoretted hydrogen would be evolved, and if this were of the spontaneously inflammable variety, it would take fire on coming into the air, but ; unless the gas receiver were full of air, this could do no harm and even if it were the results would not be serious. The only difference in different samples of carbide is in the quantity of gas they will evolve, and this difference is due to the presence of varying quantities of insoluble carbonaceous residue. This cannot be altogether avoided, as excess of carbon must bo used in the manufacture. English-made carbide is always satisfactory in this respect. Tho carbide is quite safely stored in tins, and there is no danger attending its use. Even should the generator be turned over the extent of gas which would escape would be so small as not to make an explosive mixture with the air, and, though the smell would undoubtedly he very unpleasant, no evil would result from inhaling air containing such a small quantity of acetylene. Whilst using the earlier and less perfect form of generator, the writer twice had the gas escape into the air, but in neither case was any damage done. With the modem generators this cannot happen, unless the whole apparatus be turned over—a most unlikely accident. On the whole, acetylene is certainly the best illuminant for the lanternist who is so placed that he cannot use the limelight. It is quite safe, very satisfactory for a picture up to ten or twelve feet, and rho generator is less weighty, though perhaps more bulky, than an oxygen cylinder. There is one dfcution, however, ’that should be given. Inhaled in large quantity, acetylene is poisonous, and therefore some care must be taken when emptying or cleaning the generator not to inhale the gas.