Observations on Liebig's " Organic Chemistry." 133 



wheat, rye, and oats, or 900 lb. of barley ; more than an acre 

 of land would requh'e, when assisted by the atmosphere, for the 

 richest possible crop every year. Every town and farm, he con- 

 tinues, might thus supply itself with the manure containing most 

 nitrogen, and also the most phosphates. By using at the same 

 time bones, and the lixiviated ashes of wood, the excrements of 

 animals might be completely dispensed with. 



It is difficult to remove the moisture from human excrements 

 without evaporating their ammonia. In Pans they are evaporated ; 

 and this destroys more than half of the r" *ogen, though the re- 

 mainder is still very valuable. The Chinese mix them with marl 

 in dry cakes. He advises to neutralise the ammonia with some 

 cheap mineral acid, such as sulphuric or muriatic According 

 to the Library of Useful Knowledge^ the last is best obtained by 

 mixing common salt with an equal weight of strong vitriol. If 

 this mixture were applied, when newly put together, that no 

 escape of muriatic acid might take place, muriate of ammonia 

 and sulphate of soda might be formed; sulphate of lime or 

 sulphate of potash, found both in turnips and potatoes by Dr. 

 Madden, may sometimes be formed also. When quicklime is 

 applied, it seizes on the carbonic acid of the ammonia, forming 

 carbonate of lime, and the ammonia escapes. Mild lime or marl 

 should have partly this effect also. In some marls, containing 

 alumina and potash, it might be retained beneficially. The 

 guano of South America, he says, is mostly urate of ammonia. 



The corn fields in China, he says, have no weeds, as they use 

 human excrement, while we sow weeds every year with our 

 manure. I have seen the excrement of cows, when fed on 

 potato plums, quite full of the seed of the potato. It will be 

 the same with most of the small seeds of grasses, &c. : the only 

 preventive is, co rot the manure well, and ''estroy the seeds. 



The urine of the horse contains less nitrogen and phosphates 

 than that of man. It contains only 0*7 of urea, while that of man 

 contains four times as much. The l vine f a cow, according to 

 Brande, he says, is rich in salts of potasu, and almost destitute 

 of soda. In the analysis by Brande, in Agricultural Chemistry, 

 the quantity of urea is stated as 4 per cent, much more than that 

 of a man ; reiterated analyses and experiments are perhaps needed 

 before we are certain of being correct. The urine of the swine. 

 Dr. Liebig says, contains a large quantity of the phosphates of 

 magnesia and ammonia. Pasturage is a great means of re- 

 placing nitrogen ; and, where pasturage is not followed, manures 

 containing nitrogen are more needed. The quantity of nitrogen 

 carried to the grave with every individual, he estimates at 3 lb., 

 and this is again given off to the atmosphere in the state of am- 

 monia. The greatest value, he says, shou'.I be attached to liquid 

 excrements; for every po2/«fif of ammonia, a loss o^ sixty pounds 



K 3 



