<)N WATKIi AND ITS COMPOUNDS 43 



solid state water appears ;is snow, ice, or in an intermediate form 

 lit -tween these two, which is seen on mountains covered with perpetual 

 sn<i\\ r . The water of rivers,- springs, oceans and seas, lakes, and wells 



air. But such a homogeneous mixture is formed (almost) independently of the nature of 

 the pis in which evaporation takes place; even in a vacuum the phenomenon occurs in 

 exactly the same way as in a pis, and therefore it is not the property of the gas, nor its 

 relation to water, but the property of the water itself, which obliges it to evaporate, and 

 therefore in this case chemical affinity is not yet acting at least its action is not clearly 

 pronounced. That it does, however, play a certain part is seen from the deviation from 

 Dalton's law. 



- In falling through the atmosphere, water dissolves the gases of the atmosphere, 

 nitric acid, ammonia, organic compounds, salts of sodium, magnesium, and calcium, and 

 mechanically washes out a mixture of dust and microbes which are suspended in the 

 atmosphere. The amount of these and certain other constituents is very variable. Even 

 in the beginning and end of the same rainfall, a variation which is often very considerable 

 may be remarked. Thus, for example, Bunsen found that rain collected at the begin- 

 ning of a shower contained 3'7 grams of ammonia per cubic metre, whilst that collected 

 at the end of the same shower contained only 0'64 gram. The water of the entire 

 shower contained an average of 1*47 grams of ammonia per cubic metre. In the course 

 of a year rain supplies an acre of ground with up to 5^ kilos of nitrogen in a combined 

 form. Marchand found in one cubic metre of snow water 15'03, and in one cubic metre 

 of rain water 10'07, grams of sodium sulphate. Angus Smith showed that after a thirty- 

 hours' fall at Manchester the rain still contained 34'3 grams of salts per cubic metre. A 

 considerable amount of organic matter, namely 25 grams per cubic metre, has been found 

 in rain water. The total amount of solid matter in rain water reaches 50 grams per 

 cubic metre. Rain water contains generally very little carbonic acid, whilst stream 

 water contains a considerable quantity of it. In considering the nourishment of 

 plants, it is necessary to keep in view the substances which are carried into the soil 

 by rain. 



River ivater, which is accumulated from springs and sources fed by atmospheric 

 water, contains from 50 to 1,600 parts by weight of salts in 1,000,000 parts. The amount 

 of solid matter, per 1,000,000 parts by weight, contained in the chief rivers is as 

 follows : the Don 124, the Loire 135, the St. Lawrence 170, the Rhone 182, the Dnieper 

 187, the Danube from 117 to 234, the Rhine from 158 to 317, the Seine from 190 to 432, 

 the Thames at London from 400 to 450, in its upper parts 387, and in its lower parts up to 

 1,017, the Nile 1,580, the Jordan 1,052. The Neva is characterised by the remarkably 

 small amount of solid matter it contains. From the investigations of Prof. G. K. Trapp, 

 a cubic metre of Neva water contains 32 grams of incombustible and 23 grams of 

 organic matter, or altogether about 55 grams. This is one of the purest waters which is 

 known in rivers. The large amount of impurities in river water, and especially of organic 

 impurity produced by pollution with putrid matter, makes the water of many rivers unfit 

 for n-.e. 



The chief part of the soluble substances in river water consists of the calcium salts. 

 100 parts of the solid residues contain the following amounts of calcium carbonate 

 from the water of the Loire 53, from the Thames about 50, the Elbe 55, the Vistula 65, 

 the Danube 05, the Rhine from 55 to 75, the Seine 75, the Rhone from 82 to 94. The 

 Neva contains 40 parts of calcium carbonate per 100 parts of saline matter. The con- 

 siderable amount of calcium carbonate held by stream water is very easily explained from 

 the fact that water which contains carbonic acid in solution easily dissolves calcium 

 carbonate, which occurs all over the earth. Besides calcium carbonate and sulphate, 

 river water contains magnesium, silica, chlorine, sodium, potassium, aluminium, nitric acid, 

 and manganese. The presence of salts of phosphoric acid has not yet been determined 

 with exactitude for all rivers, but the presence of nitrates has been proved with certainty 

 in almost all kinds of well-investigated river water. The quantity of calcium phosphate 

 does not exceed 0'4 gram in the river of the Dnieper, and the Don does not contain more 



