88 Recent Publications on Manures. 



oxygen and 1 of hydrogen, united to 2 atoms of carbonic acid. 

 Ulmic acid is always in humus; it is in it, he says, as sugar is in 

 the turnip or beet/ but is not it. The strength of ulmic acid is 

 so slight, that he found it took 360 grains of it to neutralise 48 

 of potash. Sawdust, peat, gum, sugar, starch, and most vegetable 

 or animal substances, will produce ulmic acid, when heated with 

 caustic potash ; and therefore it has been said by some that ulmic 

 acid is produced by the action of the potash, and is never found 

 alone or pure ; it is, say they, a product, not an educt. It is 

 not, however, always, he says, the product of the potash, but is 

 found ready formed in the soil also; as a cold solution of potash, 

 not strong or digested much with the soil, or even ammonia, will 

 produce it. The more substances are divided in the soil, and 

 exposed to the action of oxygen, the more soluble do they be- 

 come. One of the very valuable effects of the soil is to divide 

 and separate the organic matter, and expose it to action. In the 

 soluble matter, or humus of the soil, there always is ulmic acid: 

 all that is brown-coloured, and soluble in potash, is not ulmic 

 acid, but it is in it. From 108 grains of lignin, or fibre, can be 

 formed, he says, 22 of carbonic acid, 9 of water, and 77 of ulmic 

 acid. Gum, sugar, and starch, can also form ulmic acid ; and it is 

 always to be found, he says, in the dung heap, with carbonic 

 acid, carburetted hydrogen, and sulphuretted hydrogen. Sugar, 

 when fermented by itself, produces alcohol abounding in hy- 

 drogen and acetic acid, or vinegar ; but when fermented with 

 other substances, he says, other results take place. The products 

 of the mass, therefore, are not always the same as the individuals 

 composing that mass. In these compounds of masses of sub- 

 stances, when ulmic acid is produced, there is also, at the same 

 time, he says, produced a substance-like extract, denominated 

 apotheme, which, by absorption of oxygen, uniting to and ab- 

 stracting its hydrogen, becomes insoluble. It is probably, he 

 says, a modification of ulmic acid, or some compound of it; it 

 contains much carbon, and is soluble in alkalies. On the question, 

 What becomes of the gases evolved in the soil during dry weather? 

 he found that, by passing ammoniacal gas over 198*6 grains of 

 soil in a glass, it retained 3 per cent of the gas. After ex- 

 posing it to the air till no smell was found, denoting that escape 

 had ceased, the soil still retained in absorption ^ per cent, or 

 ~q part of its weight in ammonia ; which, calculating the 

 depth of the land at 6 in., the ordinary depth of ploughing, 

 would give 4 tons, or 8,960 lb., per imperial acre; capable of 

 dissolving no less than 161,280 lb. of humus. If taken to the 

 depth of 8 in. to 10 in., the ordinary depth of digging, it would 

 be much more. The whole ammonia given off, he says, by 25 

 to 30 tons of farm-yard manure (the ordinary quantity for an 

 acre), about 2,016 lb., is little more than ^ per cent of the soil, and 

 not £ part of what the soil is capable of absorbing. When he 



