42 



AGRICULTURAL CHEMISTRY. 



How much more wonderful and inexpli 

 cable does it appear, that bodies which re- 

 mained fixed in the strong heat of a fire, have 

 under certain conditions the property of 

 volatilizing and, at ordinary temperatures, 

 of passing into a state, of which we cannot 

 say whether they have really assumed the 

 form of a gas or are dissolved in one ! Steam 

 or vapours in general have a very singular 

 influence in causing the volatilization of 

 such bodies, that is, of causing them to as- 

 sume the gaseous form. A liquid during 

 evaporation communicates the power of as- 

 suming the same state in a greater or less 

 degree to all substances dissolved in it, 

 although they do not of themselves possess 

 that property. 



Boracic acid is a substance which is com- 

 pletely fixed in the fire; it suffers no change 

 of weight appreciable by the most delicate 

 balance, when exposed to a white heat, and, 

 therefore, it is not volatile. Yet its solution 

 in water cannot be evaporated by the gen- 

 tlest heat, without the escape of a sensible 

 quantity of the acid with the steam. Hence 

 it is that a loss is always experienced in the 

 analysis of minerals containing this acid, 

 when liquids in which it is dissolved are 

 evaporated. The quantity of boracic acid 

 which escapes with a cubic foot of steam, 

 at the temperature of boiling water, cannot 

 be detected by our most sensible re-agents ; 

 and nevertheless the many hundred tons 

 annually brought from Italy as an article of 

 commerce, are procured by the uninter- 

 rupted accumulation of this apparently in- 

 appreciable quantity. The hot steam which 

 issues from the interior of the earth is al- 

 lowed to pass through cold water in the 

 lagoons of Castel Nupva and Cherchiago ; in 

 this way the boracic acid is gradually accu- 

 mulated, till at last it may be obtained in 

 crystals by the evaporation of the water. It 

 is evident, from the temperature of the 

 steam, that it must have come out of depths 

 in which human beings and animals never 

 could have lived, and yet it is very remarka- 

 ble and highly important that ammonia is 

 never absent from it. In the large works in 

 Liverpool, where natural boracic acid is 

 converted into borax, many hundred pounds 

 of sulphate of ammonia are obtained at the 

 same time. 



This ammonia has not been produced by the 

 animal organism, it existed before the creation 

 of human beings; it is a part, a primary 

 constituent, of the globe itself. 



The experiments instituted under Lavoi- 

 sier's guidance by the Direction des Poudres 

 et Salpetres, have proved that during the 

 evaporation of the saltpetre ley, the salt 

 volatilizes with the water, and causes a loss 

 which could not before be explained. It is 

 known also, that in sea storms, leaves of 



mind, which would penetrate the deepest depths 

 of nature, without the assistance of the shaft or 

 ladder of the miner. This is poetry, but not sober 

 philosophical inquiry. 



plants in trie direction of the wind are 

 covered with crystals of salt, even at the 

 distance of from 20 to 30 miles from the 

 sea. But it does not require a storm to 

 cause the volatilization of the salt, for the 

 air hanging over the sea always contains 

 enough of this substance to make a solution 

 of nitrate of silver turbid, and every breeze 

 must carry this away. Now, as thousands 

 of tons of sea water annually evaporate into 

 the atmosphere, a corresponding quantity 

 of the salts dissolved in it, viz. of common 

 salt, chloride of potassium, magnesia, and 

 the remaining constituents of the sea water, 

 will be conveyed by wind to the land. 



This volatilization is a source of con- 

 siderable loss in salt works, especially where 

 the proportion of salt in the water is not 

 large. This has been completely proved at 

 the salt works of Nauheim, by the very 

 intelligent director of that establishment, M. 

 Wilhelmi. He hung a plate of glass be- 

 tween two evaporating houses, which were 

 about 1200 paces distant from each other, 

 and found in the morning, after the drying 

 of the dew, that the glass was covered with 

 crystals of salt on one or the other side, ac- 

 cording to the direction of the wind. 



By the continual evaporation of the sea, 

 its salts* are spread over the whole surface 

 of the earth ; and being subsequently car- 

 ried down by the rain, furnish to the vegeta- 

 tion those salts necessary to its existence. 

 This is the origin of the salts found in the 

 ashes of plants, in those cases where the 

 soil could not have yielded them. 



In a comprehensive view of the phe- 

 nomena of nature, we have no scale for 

 that which we are accustomed to name, 

 small or great; all our ideas are proportioned 

 to what we see around us, but how insig- 

 nificant are they in comparison with the 

 whole mass of the globe! that which is 

 scarcely observable in a confined district 

 appears inconceivably large when regarded 

 in its extension through unlimited space 

 The atmosphere contains only a thousandth 

 part of its weight of carbonic acid ; and yel 

 small as this proportion appears, it is quite 



* According to Marcet, sea- water contains in 

 1000 parts, 



26-660 Chloride of Sodium. 

 4-660 Sulphate of Soda. 

 T232 Chloride of Potassium. 

 5'152 Chloride of Magnesium. 

 0-153 Sulphate of Lime. 

 According to M'Clemm, the water of the North 

 Sea contains in 1000 parts, 



24-84 Chloride of Sodium. 

 2'42 Chloride of Magnesium. 

 2'06 Sulphate of Magnesia. 

 1'25 Chloride of Potassium. 

 1-20 Sulphate of Lime. 



In addition to these constituents, it also con- 

 tains inappreciable quantities of carbonate of lime, 

 magnesia, iron, manganese, phosphate of lime, 

 iodides and bromides, silica, sulphuretted hy- 

 drogen, and organic matter, together with ain 

 monia and carbonic acid. (Liebig's Annalen der 

 Chemie, Bd. xxxvii. s. 3.) 



