HYGIENE OF GAS.

New Zealand Herald, Volume XLIV, Issue 13626, 20 December 1907, Page 3

HYGIENE OF GAS.

USE OF GAS FROM A HYGIENIC STANDPOINT. Continuation of lecture by Professor Vivian B. Lewes. F.1.C.. F.C.S.. Professor of Chemistry at the Royal Naval College, Greenwich. " ; ' THIS VALUE OF DIFFUSION. Carbon dioxide is a gas considerably heavier than air so much so, indeed, that it cau be poured from one vessel to another almost nKe a liquid. But, like all other gases, it is expanded by heat; and as tho foul air coming from the lungs, and containing some five per cent, of carbon dioxide, is at practically the temperature of the bodyi.e., 98 degrees Fahr.— it at once rises towards the ceiling, while the products of combustion from tho gasburner, being at a still higher temperature, also rush up to' this point, so that the foul air is always to be found at the top of tne room. One might think this foul air when cooled down would descend into the room again. But here conies into play the process of diffusion— process by which gases instead of arranging themselves, like other forms of matter, according to their weight, undergo a mingling or diffusion, the rate of which is dependent upon their weight; a light gas mixing rapidly with others, while a heavy one diffuses more slowly. , It is found that, once mingled, the gases remain in perfect admixture ; so that in the present case the heavy carbon dioxide will not again separate from the air into which it has become diffused.

This so-called diffusion of gases can be, and is, experimentally shown in many ways, and will take place with even greater rapidity through porous solids than when the gases are left simply in contact with each other; and as the plaster of the ceiling and the bricks or other building material of which our walls are composed are full of minute openings or pores, they allow gases to .diffuse through with considerable ' rapidity—the force of diffusion being aided by a second force called capillarity. The result is that, even though the ventilation of a room has been neglected, and no proper outlet has been arranged at the top for drawing off foul gases, diffusion through the celling and the walls in the upper part of the room provides so rapid an egress for the hot gases that they have not time to mingle with the air in the lower portion of the room, while fresh air is being constantly drawn in through every crack and crevice left by the jerry builder. V

GAS AS AN AID TO VENTILATION*. An interesting series of experiments which I have made shows conclusively that taking an ordinary dwelling-room lighted by gas and then the same room lighted by electricity, the air of the lower portion of the room, if one or two people only are present, is as pure with gas lighting as with electric lighting; while if a large number are present the advantages are enormously in favour of gas the air with electric lighting becoming rapidly so organically impure as to be positively dangerous to health. Distribution of carbon dioxide in the air of a dwelling-room (capacity 2700 cubic feet) with gas and electric incandescent lighting: — • GAS LIGHTING. Two Welsbach C" burners (on ' pendant), each consuming 4 cubic feet of gas per hour, and giving 140 candles. Carbon Dioxide. Temperature, Parts per 10.000. Deg. Pahr. Outside air 0.03 61.0" Between joists 0.06 66.0 Ceiling level ... ... 0.44 74.7 Breathing level ... 0.05 63.0 ELECTRIC LIGHTING. ' Three 16 Candle-power Incandescent. Lamps., ' • Carbon Dioxide. Temperature, . Parts per 10,000. Deg. Fahr. Outside air 0.03 61.0 Between joists 0.04 61.5 it, Ceiling level . ... ... 0.09 ' 62.5 Breathing level ... *0;06 . 61.7 If a h'umber of people are in a room ; the - organic exhalations as well as- the carbon dioxide and water vapour evolved during respiration rise, audi reaching the level of the gas-burners, are rapidly swept up to the ceiling by the "rusli of hot gas from the burner flame, and heat destroying and charring a large proportion of the germs. The hot air reaches the ceiling, and diffuses through the plaster and walls in the upper part of the room and in doing, so the charred organic matter is left behind, filtered off on the surface. of the plaster, and rapidly causes thajt discolouration of the ceiling which is, invariably found in a town atmosphere above the . gas-burner, and which is often wanting with country air. That this is the case is amply verified by the fact that if beams are present at the back of the plaster diffusion is prevented at these joints, and their position is plainly mapped out on the discoloured surface. When the room with its occupants was lighted by electric light there was no rapid Uiprush in this way of the products to the ceiling; and %ia organic impurities and carbon dioxide .leaving at body temperature remained diffused, throughout the whole of the atmosphere of the room, causing a far more rapid fouling of the air and .injury to health. If such a room were entirely left for its ventilation to diffusion through the walls it would soon acquire that sour smell which is noticeable in many rooms of the poor, in which, in order to keep in the v warmth derived from their own bodies, all ventilation. is cut off. This smell is due to the decomposition of organic matter filtered off dupnig diffusion by "the Wall surface and undergoing putrefactive .decay, giving ..the offensive odour, the "only way to get rid of which is to strip the paper from the walls and lime-wash them as well as the ceiling. Then, and. Alien only, does, the smell pass away. . When, however, this same diffusion through the ceiling and upper part of the walls of the room takes place in a gaslighted room, this unpleasant human smell, so characteristic of the " tube" railways, is never detected, as the small quantity of sulphur compounds present in the gas (as was shown by researches of Mr. Otto Hehner and Dr. Rideal) is largely absorbed and fixed by the lime and lime salts present, and acts as a disinfectant, destroying all. forms of germ life. Here, again, the hygienic superiority of gas is manifest, as in a gaslighted room or hall not only, are. the germs present in the air, and often of an infectious character, destroyed and burnt up by the flame itself, but also undergo destruction and disinfection from the trace of sulphur dioxide present in the products of combustionan action which is entirely wanting when the illumination is due to incandescent electric light. An interesting point also brought out by the experiments I have made is that it is really the position of the gas-light above the level of the head in the chandelier which causes this hygienic advantage, and* that if the gas is burning in - tablelamps the cooling of the products' in their passage'up to the ceiling largely does away with the ceiling action, and the air of the room may become as foul as when it is unlit, or lighted'by electric light; ""