Chemistry / by George Wilson.

  • George Wilson
Date:
1857
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry / by George Wilson. Source: Wellcome Collection.

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    upon temperature, so that it varies with latitude, the season, region of the atmosphere, See. 398. The quantity of ammonia is so small, that it has not hitherto been found possible to determine its relative quantity. It occurs in the atmosphere, combined with carbonic acid, as carbonate of ammonia; and with nitric acid, as nitrate of ammonia. 399. The presence of oxygen in the atmosphere is proved by combustible bodies becoming converted into oxides when made to burn in it. Thus hydrogen becomes water, the oxide of that gas. 400. The presence of nitrogen is demonstrated by the result of combustion in confined portions of air, as we have mentioned whilst describing the method of obtaining free azote. 401. The relative quantity of these gases may be most simply ascertained by introducing into a tube, graduated into a hundred equal parts, the same number of measures of air. A piece of phosphorus attached to a wire is then to be passed up into the confined portion of air, the tube all the while being kept vertically in the pneumatic trough with its mouth downwards, and under water. The arrange- ment is to be left undisturbed for twelve hours, during which period the phosphorus, though not Fig. 38. kindled, slowly combines with the oxygen of the ail’, forming an acid which the water dissolves. At the end of the time specified, the phosphorus may be withdrawn, and the volume of gas which remains observed. The water should rise through 21 spaces, replacing the oxygen with- drawn, and leave 79 volumes of nitrogen. 402. The presence of carbonic acid in the atmosphere is demonstrated by leaving a shallow vessel containing lime- water in the open air. The lime-water rapidly becomes turbid, owing to the combination of the carbonic acid with the lime to form the insoluble carbonate of lime, chalk (Ca0,C02). 403. To detect ammonia, air must not be taken, but rain- water or snow, both of which, in falling through the atmo- sphere, carry with them the ammonia diffused through it. Several gallons of rain-water must be employed, or many pounds of snow. The rain, or melted snow, is placed in a still, and a fourth part of it distilled over. The ammonia (or rather its carbonate), which is volatile, accompanies the water, which first rises in vapour. To this, after its condensation, a little muriatic acid is added, which combines with the am-
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