OHEMI8TB7. 



[NITI: 



magnecia, or Epsom aalU, is a common constituent ol 

 in MIL- ml waters ; and common salt U generally found 

 ai*> in various pro]irti<>na. The water of the ocean con- 

 tain* numerons tall*, a* we have already mentioned ; 

 and it ha* been lately averted that silver U also present 

 to a alight extent, which, however, in the aggregate, 

 would frm a prodigious quantity of that metal in the 

 ocean. In tome part* of Cornwall, the water flowing 

 from the mine* U largely impregnated with cop]>er ; ami 

 the turtal u extracted therofrom by throwing into the 

 streams craps of old iron, such as the debrvt of the pots 

 and pans of London, which are sent to the mineral dis- 

 trict* in Urge quantities for tliat purpose. 



On the continent of Europe, especially in some parts 

 of Germany, mineral springs abound ; and such places 

 are sought for by invalids for the purpose of partaking 

 of the waters. We may remark, that chemical analysis 

 has so far succeeded in detecting the presence of all the 

 alts contained in such waters, as to permit of their manu- 

 facture in any place ; and there is scarcely a doubt that 

 more Seltzer water, <kc., is manufactured yearly in 

 London than has ever been imported from the original 

 and recognised source. 



With respect to the value of mineral waters, in a 

 medicinal point of view, much exaggeration has doubtless 

 been made. Change of scene and society, pure mountain 

 air and exercise, have a more beneficial effect on the 

 human system than any medicament which can be ad- 

 ministered ; and to such may be rather assigned the im- 

 proved state of health which the valetudinarian experi- 

 ences on visiting a spa, than to the effect of its waters of 

 which he partakes, although they may exert an assistant 

 office. 



The organic impurities of water is a subject of the 

 deepest importance, in a sanitary point of view. In 

 direct proportion as organic matter of any kind is present, 

 so the tuners of such water for drinking purposes 

 diminishes. In many districts moss is gathered as 

 the water runs down the mountain sides, and along 

 the banks of the stream ; and this is readily noticed if 

 the water be allowed to drop on a rough stone surface, 

 which will then become covered with a green coat of 

 vegetable matter. Such generally occurs in moun- 

 tainous districts. In towns, the wells often contain 

 animal matter, and its products in solution ; and in the 

 city of London, there are wells which are simply the 

 result of the drainings of the churchyards to which they 

 are adjacent. The water obtained from such sources has 

 a very pleasant and cooling taste, from the presence of 

 nitre ; this arising from the nitrogen afforded during the 

 decomposition of animal matter. If such water be ex- 

 posed to the atmosphere during summer-time for a few 

 days, it will give off a most offensive smell Indeed, 

 persons partaking of it are simply imbibing the products 

 of the decomposition of the bodies of their ancestors, in 

 a soluble form ; and the effect is often manifest in the 

 production of diseases, such as diarrluna and cholera. 

 Districts supplied with water from such sources are 

 certain to be the most unhealthy during sumraer-time, 

 and are fitting fields for the ravages of the complaints we 

 have mentioned. 



We may here call attention to what we believe will 

 eventually become a source of great danger to the health 

 of Urge towns. Wo refer to the position of cemeteries, 

 so commonly found in the suburbs. London itself is 

 encircled with these burial-places, nearly every one of 

 which is located on a sandy soil Tons of human remains 

 are yearly deposited in them ; and, as these decom- 

 pose, the soluble matter will be carried away with the 

 percolating water, afterwards to bo pumped up for drink- 

 ing and other purposes. Of course, many years will be 

 required to pass away before the result* we have hinted 

 at take place ; but eventually, chemical analysis and 

 sanitary reports will more than likely show, that the 

 proximity of burial-grounds to Urge cities will produce 

 an evil of no ordinary, and, perhaps, of incurable mag- 

 nitude. 



In animal and vegetable life, we need not remind our 

 'dor* that water exorcises the most important func- 



tions. It fills the cells of the tree with sap, and courses, 

 in the form of blood, through the vi-ini of the .iniin.il. 

 By moans of it, the food is conveyed, in a suitable form, 

 to afford flesh and muscle ; the salts, which produce 

 bone, are dissolved by it, and are presented in a suit il .],- 

 condition for that purpose. We must, however, dismiss 

 this, and many other such matters, until we more fully 

 treat on organic and agricultural chemistry. 



Hydrogen combines with oxygen, in the proportion of 

 one equivalent of the former to two of the Utter, to 

 form what U called the peroxide of hydrogen ; symbol, 

 HO; equivalent 17. This, like water, is a liquid ; 

 and, although a very interesting production in a che- 

 mical point of view, has no general use or interest. It 

 is prepared by a somewhat intricate and difficult process, 

 by means of peroxide of barium and hydrochloric acid. 

 The peroxide of hydrogen and chloride of barium are 

 produced, and the baryta is precipitated by sulphuric 

 acid, the chlorine being removed by means of a salt 

 of silver. The combinations of hydrogen with chlorine, 

 iodine, bromine, and fluorine, have been already noticed : 

 those with other substances will be duly mentioned as 

 we proceed. 



NITROGEN. 



IN our former pages, we have spoken at some length 

 on the qualities of one of the gases present in the 

 atmosphere, and showed that oxygen is a powerful sup- 

 porter of combustion, and essential to the existence of 

 all animate bodies. The air, however, contains another 

 gas, by means of which the active properties of oxygen 

 are modified, so as to render them suitable to the 

 organisation and circumstances of vitality, and to the 

 properties of this gas. Nitrogen, and its leading com- 

 pounds, we must now draw attention to. Its symbol is 

 N ; equivalent =- 14 ; and its specific '972 ; air <= 

 1-000. 



The properties of nitrogen are almost entirely of a 

 negative character. It does not support combustion ; 

 has no smell or taste ; is scarcely absorbable by water. 

 It derives its name from nitre, of which it is a con- 

 stituent ; it is occasionally called azote, from the fact 

 that animals cannot breathe it in a pure state. It has, 

 however, no direct poisonous qualities ; and fatal effects 

 resulting from inspiring it, arise from the absence of 

 life-sustaining powers. It, however, exerts great in- 

 fluence in animal life, as it forms a constituent of flesh, 

 anil various compounds produced or consumed by ani- 

 mals. It is a chief constituent of ammonia and nitric 

 acid ; and many products of the vegetable kingdom con- 

 tain it as an essential element. 



The readiest mode of procuring nitrogen for the pur- 

 poses of experiment, is that of removing the oxygen of 

 atmospheric air by means of burning phosphorus. The 

 atmosphere is not a chemical compound in the strict 

 sense of the term, but rather a mixture of oxygen and 

 nitrogen gases ; and hence, phosphorus and other burn- 

 ing bodies readily remove the oxygen by combining 

 with it, leaving the nitrogen free. 



Es.jtcrimtnt 41. Place a small piece of phosphorus on 

 a piece of cork floating in a basin of water ; and having 

 ignited the phosphorus, invert over it a tall glass jar 

 full of air, pressing the mouth of the vessel beneath the 

 surface of the liquid. A few bubbles of air will at first 

 escape, owing to the expansion of the air by heat. 

 Eventually, however, the water will rise inside the glass 

 jar to the extent of about one-fifth of its capacity. The 

 white fumes of phosphoric acid produced by the com- 

 bination of the phosphorus with the oxygen of the air, 

 will be gradually absorbed, and a colourless gas will be 

 left, which can then be removed into another and smaller 

 glass jar, by means of the pneumatic trough, in the 

 ordinary manner. There are other means of procuring 

 nitrogen, which, however, have no advantage, in a prac- 

 tical point of view, over that above described. 



AV/ii'rimcnt 42. Having filled a small glass jar with 

 nitrogen, remove it, mouth downwards, from the tn.ii -1^ 

 and introduce into it a lighted taper, which will l-o 



