144 Observaiions 0)i Liebig's " Orgajiic Chemistry.^' 



be deprived of its chlorine by degrees, if mixed with water 

 containing oxygen ; and it may thus, gradually, come to be 

 beneficial in a soil : to some plants it is useful as forming a con- 

 stituent. Dr. Madden says it sometimes, in a moist state, acts 

 on the lime in the soil, forming muriate of lime and carbonate 

 of soda ; but is apt to resume its original form again. Nitrate 

 of soda is formed largely, by natural processes, on the surface of 

 the soil in Peru, &c. ; and nitrate of potash (saltpetre) in the 

 same way in India; and both are now much used as manures. 

 Heat is necessary in forming nitric acid, and a basis of lime ; 

 it is, therefore, most readily formed in warm climates, and unites 

 to the bases of potash and soda according as they are found ia 

 the soil. Nitrate of lime is also generally found mixed with 

 these salts. They form an article of commerce from warm 

 countries, and are manufactured in France and other places 

 in beds in the open air. In some trials recently made by Archi- 

 bald Hamilton, Esq., of Carcluie, (to whom this county, and 

 agriculture in general, are so much indebted for setting an 

 example in improvements,) on his estates at Roselle, near Ayr, 

 both substances appear to have succeeded well. On fields in 

 which these salts were sprinkled, at the rate of IJ cwt. per acre, 

 while parts of the same fields were sprinkled with common salt, 

 and part left without any application of salts, the increase of pro- 

 duce where the nitrates were sown was astonishing on the grass of 

 pasture, and the straw and grain of wheat and oats; turnips, 

 potatoes, and most other farm produce, were also benefited : the 

 common salt produced no effect. The benefits must have arisen 

 from the nitrogen supplied to form ammonia, and the solvent 

 power of the bases, if i*eturned. In parts of the fields where 

 the oxides of iron abounded (as stated at the time in the Ayr 

 Advertiser) no benefit was derived. From the great affinity of the 

 protoxide of iron for salts, nitrate of iron would be formed, by 

 the iron separating the nitric acid from the potash and soda. 

 Dr. Thomson says, when the protoxide gets more oxygen from 

 the air, it forms peroxide, and the acid is set free : the nitric 

 acid would thus likely be lost in the air, and the good effects of 

 its nitrogen never felt. From the great affinity between iron 

 and the acids, it is very hurtful, and, if sulphate of iron is 

 formed, poisonous. Carbonate of lime (chalk, or mild lime) 

 converts the iron into carbonate of iron, and the sulphate of 

 iron into sulphate of lime. The salts of iron are so susceptible 

 of change, that their bad effects may not be always felt in the same 

 way. Oxides of iron exist in all soils, and are not detrimental 

 till their quantity, giving tlie subsoil a red and glistening ap- 

 pearance, shows they are in excess. Being the most general 

 colouring matter, they are very prejudicial to the colours of 

 fine tulips and other flowers, when in excess. Most ditches, if 



