Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/246

234 GUANO 1874 336,476 1875 373,688 1876 378,663 1877 310,042 Tons. Australia 1 , 168 British West Indies 1,050 St Helena 981 Chili 503 United States 458 Other places .. 2,545 gave over 2 million tons available for commerce, but this j figure presumably includes all varieties, both nitrogenous and pbosphatic. Most of the guano lately and now exported , comes from the following groups of islands, or places on the coast Macabi, Huanape, Ballestas, Punta de Lobos, Pabellon de Pica, and Huanillos, and, since 1877, particu larly from the last two localities. In the article AGRICULTURE (vol. i. p. 347) some statistics of guano imports were given. According to the British Consular Reports (1878, No. iv. pp. 525-539) the quan tities of Peruvian guano sold of late years were, in tons 1869 574,790 1870 451,501 1871 363,200 1872 402,097 1873 342,425 The amounts of Peruvian guano taken by different countries during 1876 and 1877 were as follows : 1876. 1877. England and her colonies 1 30, 598 100, 954 France and her colonies 102,165 72,067 Germany 63,724 23,455 Belgium 48,246 71,473 Spain 28,359 23,455 Italy 3,594 5,440 Holland 1,977 3,658 In 1872, when the number of countries contributing guano was very large, the imports into the United King dom were as follows : Tons. Peru 74,401 Pacific Islands 17,475 Bolivia 14,068 West Coast of Africa 3,201 Dutch West Indies 1,562 Brazil 1,232 The following are amongst the more obvious character istics of good Peruvian guano. Although at the present time it is by no means of uniform appearance or of constant composition, yet it may be stated that the best qualities, which most closely resemble the former supplies from the Chinchas, are light in colour, do not weigh much more than GO ft) per bushel, are friable, and do not cohere strongly when pressed between the fingers. Small soft lumps are often observed in good samples ; when these are broken a white or pale-coloured substance is seen in the centre. This lighter-coloured matter contains carbonate and other am- moniacal salts ; in some adulterated samples its appear ance is imitated by means of gypsum. The hard lumps found in guano are of very varying composition, some being highly phosphatic and others highly siliceous. The ash left on burning a good Peruvian guano is white or grey ; a red ash generally indicates adulteration with ochre or ferrugin ous earth. An unusual proportion of water commonly points to damage by sea-water or rain, a kind of injury which is the more serious, since it is usually accompanied by a con siderable loss of ammonia. If more than a mere trace of chlorine be found in a sample of guano, damage by sea- water may be suspected. Although a good guano com monly contains more than half its weight of organic matter and of other substances driven off by a red heat, yet when a still larger quantity of such volatile matters is found their presence may be, and often is, a sign of admixture with peat. Guanos have been often submitted to analysis, much more frequently, however, for the sake of determining their agricultural value than their precise chemical components. Their worth as manure practically depends, so far as analysis can show, upon their richness in nitrogen and phosphates. The nitrogen, we know, exists in several forms, of which uric acid or rather urates, with salts of ammonia (the urate, oxalate, carbonate, and phosphate), are the most important. But besides these compounds a peculiar base or animal alkaloid known as guanine (C 5 H 5 N 5 0) is present in most samples of Peruvian guano ; it is not unlikely that the nitrogen of this body is capable of direct assimilation by plants. A considerable though variable quantity of nitrates and nitrites has been recognized in some guanos, ranging, when expressed as potassium nitrate, from no more than y 1 ^ per cent, up to 5 and even 6 per cent. Other nitrogenous compounds present are those indeterminate substances which originate from the decay of the osseids of bone, skin, cartilage, and feathers, and of the proteids of flesh. These intermediate products of decay are ultimately resolved into ammonia salts and nitrates. Some guanos, notably those of the West-African coast (Ichaboe, for example), contain many un- decomposed feathers, which cannot possibly yield their nitrogen to vegetation for some time. On this account less than half oi the 8 to 12 per cent, of so-called "potential " ammonia in these guanos is as effective as that in the genuine Peruvian samples. The phosphates of guano are numerous, including tricalcic, dicalcic, ammonio-magnesic, and ammouic phosphates. The solubility of great part of the phosphates in guano helps to make its action more intense and immediate ; as much as 10 to 13 per cent, of phosphorus pentoxide has been found to be soluble in some instances. Such is said to be often the case with the guano of Tarapaca; Baker Island and Jarvis Island guanos are similar. This solubility arises partly from the composition of the phosphates present, some of which are naturally moderately soluble in ordinary water ; but it arises partly also from the presence of ammonium oxalate, by which the solubility of the calcic phosphates is increased. The carbon dioxide which the decaying organic matter of guano continually evolves also aids in effecting the solution of those phos phates which are not soluble in pure water. As at least part of the nitrogen of guano exists in the form of the volatile carbonate, it will be found that this manure deteriorates sometimes very much on being kept. One sample of Cliincha guano imported in 1865 contained nitrogen equal to 20| per cent, of ammonia ; of this 10| per cent, was lost when the guano was exposed to the heat of boiling water, and 9| per cent, when the sample was merely kept for a year in a powdered condition in an ordinary bottle. With so strongly ammoniacal a guano as this, the fixation of the volatile nitrogenous compounds by means of an acid is highly desirable. Oil of vitriol is employed ill different propor tions and in different ways for this purpose. About 5 or 6 Ib of oil of vitriol diluted with water and mixed with sand or peat may be added to each cwt. of guano. Such a process was patented in 1859 by Dr Richardson of Newcastle. In this way the ammonia of the volatile carbonate is fixed in the form of sulphate, the oxalates and phosphates of the guano remaining unaffected. But sometimes, as in the manufacture of "dissolved guano," a larger quantity of 011 of vitriol is used say 25 to 30 Ib to each cwt. of raw guano. In this case a kind of rich superphosphate is obtained in which 20 per cent, or thereabouts of "bone-phosphate made soluble" is present in association with nitrogen equal to 9 or 10 per cent, of ammonia. Such a preparation is OhlendorfF s dissolved Peruvian guano, while "sulphated" and "ammonia-fixed" guanos contain less oil of vitriol, and generally some inert substance like saw dust, which reduces their concentration as manures considerably. " Phospho guano" is in reality a superphosphate made from Mejillones or other phosphatic guano, and enriched by the addition of ammonium sulphate. This Mejillones (Bolivian) guano contains about per cent, of nitrogen and 55 per cent, phosphates. " Native guano " is a term applied to the dried and prepared sludge or deposit obtained in the treatment of town sewage by the "A. B.C." process one of the many precipitation processes now in use. It has little in common with true guano. " Fish guano" is prepared chiefly from the refuse of the cod of the Newfoundland and Nor- wegian fisheries. It is rich both in nitrogen and in phosphates, often containing 8 per cent, of the former and 30 per cent, of the latter ; but its oily nature causes its action as manure to be un certain and slow. Although it is usual and convenient to classify guanos into two groups according to their richness in nitrogen or phosphates respect ively, there is no sharp line of demarcation between these classes. Indeed the guano from a single spot may show every gradation from nitrogenous to phosphatic. For instance, three samples taken from a deposit at Punta de Lobos gave amounts of nitrogen corresponding to the following percentage of ammonia in the several layers surface, 81 per cent.; middle, 3 15 per cent.; deepest, 15 67 per cent. Three samples from another working in the same huanera gave these figures 3 per cent, ammonia at 8 feet, 8 per cent, at 20 feet, and 12 at 40 < "et. A cargo averaging 12 per cent, of potential ammonia, that is, containing an amount of nitrogen which, if expressed as ammonia, equals 12 parts in the hundred of guano, may be regarded as satisfactory ; but immense quantities of guano are now exported from Peru, containing not more than 8 or 10 per cent, of ammonia. And there are lower qualities still, with 6 to 8 per cent, of ammonia ; and these pass into more phosphatic varieties, with but little organic matter and nitrogen, but yet from their softness and fine state of division capable of being applied, without previous mechanical or chemical treatment, to the land. But when we are dealing with what are called "rock" or "crust" guanos, we not only have an almost

complete absence of nitrogen and of organic matter, but the hard-