SANITARY SCIENCE.] 



CHEMISTRY. 



427 



abundantly produced in the lungs, and is, of course, 

 exhaled as the breath is exspired. With this, a con- 

 siderable amount of foetid animal matter is also exhaled, 

 which adds to the impurities of the surrounding air. If 

 a person sit in a room destitute of arrangements for ven- 

 tilation, he must, after a time, re-breathe these poisonous 

 exhalations, and by so doing vitiate the blood, which 

 depends on the supply of pure air for its oxygenation. 

 The close smell of bedrooms in the morning, after one or 

 more persons have slept in them, is caused by these 

 exhalations ; and the foetor of alleys and courts, inhabited 

 by the poorer classes, is due to the same cause, aided, 

 however, by imperfect sewers, closets, <fec. 



Now the atmosphere, in its normal condition, contains 

 only from four to six parts of carbonic acid in ten thou- 

 sand of air. In unventilated rooms this proportion 

 enormously increases ; and an idea of this may be gained 

 from the following example of a boys' school, extracted 

 from a Parliamentary Report : 



Capacity of room . . -22, 140 cubic feet. 

 Number of boys present . . 164 

 Carbonic acid present in the air \ 23 '71 

 of the room after having been > ^^fjfi 

 occupied 2 hours 

 Thus we see that the proportion of carbonic acid to 

 that of air had increased from 5 to nearly 24 parts per 

 10,000, or nearly five times its normal quantity. How- 

 can we wonder, then, that fevers abound in crowded 

 localities when such palpable facts are presented to us. 

 It must be borne in mind, also, that besides the carbonic 

 acid afforded, animal matter, other gases, and impure 

 aqueous vapour are produced in such cases. The pre- 

 sence of these soon become evident from the languor into 

 which the children fall ; and then the physical evils re- 

 sulting from breathing impure air, exert a visible and 

 undeniable influence. 



Defective drainage is another cause of impure air, and 

 in many case* a most fatal one. The sewers, of course, 

 carry off every species of excreta and waste from our 

 houses. These substances all mix together, and mutually 

 decompose, giving off many hydro-carbons, sulphuretted 

 hydrogen, and other deleterious substances. When the 

 xmnection between the house-drain and the main sewers 

 is defective, these gases will enter the house, especially 

 when the barometrical column is falling ; hence arises the 

 "smell of drains" just previous to wet weather. Defec- 

 tive drainage and typhoid diseases are always to be found 

 concomitant ; and the only effective remedy lies in re- 

 moving the cause of the evil. 



DisiNFKCTANTs We may here conveniently refer to 

 substances which have been used as disinfectants, omitting 

 tuch as pastiles, perfumes, <fcc., which merely mask, but 

 do not remove, pernicious exhalations. Chloride of lime, 

 chloride of zinc, carbolic acid, caustic lime, and charcoal, 

 are the most effective that can be used, consistent with 

 abundance of supply, and consequent cheapness. 



The two chlorides are of great value, because they de- 

 compose, sooner or later, most of the hydro-carbons in 

 sewage gases ; they are easily applied, and are very- 

 cheap. Carbolic acid and lime are not so fit for domestic 

 use as those we have named, but can be employed on 

 the large scale. The former may be cast down sewers ; 

 whilst the lime is suitable for covering graveyards, and 

 any places whence effluvia are given off. Of late years, 

 immense quantities of lime have been thrown into that 

 great common sewer, the River Thames, during the 

 summer months, and with the most beneficial effect. 



Charcoal, whether as obtained from peat or other sub- 

 stances, is of great value. It is readily applied, and is 

 of slight cost. Some years ago it was proposed, by Drs. 

 St.t n house and Watson, to purify the air supplied to 

 hospitals, by passing it over trays of charcoal, or charcoal 

 containing platina in a minute state of division. The 

 following extract from Dr. Watson's remarks, gives the 

 rationale of the method, and also affords some instances 

 in which charcoal may be usefully applied : 



" Charcoal, as is well known, has the power of absorb- 

 ing various gases in large quantities, and, perhaps, few 

 mure readily than those which arise during the decay of 



dead animal and vegetable substances. But charcoal 

 does something more than simply absorb ; for it is evident 

 that, if it possessed no other property, a point would 

 shortly be reached, when, having become quite saturated, 

 it would cease to act. Charcoal, then, has another power 

 in addition to that of absorption ; and for the illustration 

 of this I would refer to the following striking experi- 

 ment : Certain dead animals were placed in an open 

 box, and covered with a layer of roughly-pounded 

 wood charcoal, rather less than three inches in thickness, 

 and all the decomposible portions disappeared more 

 rapidly than if they had been buried in the ordinary 

 way. Moreover, the boxes containing these dead animals 

 were kept for many months in a room in which several 

 persons were employed during the day, but still no dis- 

 agreeable effluvia were detected, and health remained 

 unaffected. 



" All decaying animal and vegetable matters give off, 

 during decomposition, foetid and deleterious gases, which, 

 in the end, tell as fatally upon the human constitution 

 as does the bite of a viper, or the most insidious poison 

 known to the chemist ; and the animals referred to in 

 these experiments formed no exception to this rule a 

 fact which could be readily ascertained by removing a 

 portion of the charcoal so as to get nearer to the putrid 

 mass below. From this, therefore, it follows, that not 

 only does the charcoal hasten decomposition, but that 

 those deadly gases that are constantly being given off, 

 become, in their passage through the charcoal, converted 

 into inodorous and comparatively harmless ones 



" The explanation of this peculiar result is simple and 

 very beautiful. Charcoal is an extremely porous sub- 

 stance, presenting through its mass an almost incredible 

 amount of surface ; and upon this depends its power of 

 absorbing various gases in large quantities. The oxygen 

 of the air is the great vivifier of nature. The deadly 

 emanations given off by decomposing matters are in what 

 is called a ' low state of oxidation ;' that is, they contain 

 a comparatively small proportion of oxygen. Combine 

 them with, or force them to take up, more of this purify- 

 ing element, and the point is gained : that which, perhaps, 

 an instant before would have proved most hurtful if 

 breathed, becomes now almost entirely resolved into 

 comparatively harmless combinations. 



"Now charcoal contains within its pores a very large 

 proportion of oxygen, amounting to rather more than 

 eight times its bulk. As already shown, it absorbs the 

 various putrid gases with avidity, and in this way they 

 are brought into intimate contact with the condensed 

 oxygen existing in the charcoal, and the result is as has 

 been described. 



" Such, then, is the action of common charcoal in 

 dealing with the foetid gases of decomposition. It not 

 only absorbs but destroys them ; that done, it gives out 

 the resulting comparatively harmless products ; room is 

 made for more oxygen from the air, and more of these 

 bad gases from whatever source, and thus the process 

 ceaselessly goes on. In this manner the charcoal is, so 

 to speak, constantly purifying itself ; and, under ordinary 

 circumstances, with occasional exposure in front of a 

 large fire, or to the sun's rays, its powers remain intact 

 for an almost indefinite period." 



For domestic purposes, as the above extract will show, 

 charcoal is of great use. It may be employed either in 

 powder or in pieces of about the size of a pea, and, in 

 that state, should ba thrown over the object to be dis- 

 infected. 



VENTILATION. This subject, although its end is of a 

 purely chemical character, more properly appertains to 

 the Laws of Heat ;* .we shall, therefore, confine our re- 

 marks to general principles only. 



The gases given off from the lungs, are nitrogen and 

 carbonic acid, in a heated state. The former has a 

 specific gravity of 0'97, whilst the hitter has that of 

 1 '524. We should hence suppose, at first, that the nitro- 

 gen would rise in the air of a room, and the carbonio 

 acid would fall to the lower parts ; but this never hap- 

 in the section on Heat, this subject Is treated on in considerable 

 practical detail. 



