The following analyses of a sample of Chincha island guano by Karmrodt[191] will illustrate this. (Sample dried at 212° Fahr.):—
1. Constituents easily soluble in Water.
| Urate of ammonium | 12.74 |
| Oxalate of ammonium | 13.60 |
| Nitrogenous and sulphurous organic substances | 3.61 |
| Ammonium-magnesium phosphate | 4.00 |
| Ammonium phosphate | .90 |
| Ammonium sulphate | 1.82 |
| Ammonium chloride | 1.55 |
| Potassium sulphate | 3.30 |
| Sodium chloride | 2.44 |
| 43.96 |
2. Difficultly soluble in Water, soluble in Acids, Alcohol, and Ether.
| Uric acid | 21.14 |
| Resin | 1.11 |
| Fatty acids | 1.60 |
| Nitrogenous and sulphurous organic substances | 2.29 |
| Calcium phosphate | 18.22 |
| Phosphate of iron | 1.04 |
| Silica | .64 |
| 46.04 |
In the above analysis it will be noticed that none of the ammonia is present as carbonate. In most samples, however, of Peruvian guano, the ammonia in this form amounted to from 1 to 2 per cent. In the inferior qualities, chiefly those which had been subjected to the action of water, and consequently of fermentation, to a certain extent, this form of ammonia was found to be most abundant. Such guanos were most liable to loss of nitrogen by volatilisation.
The older Peruvian guano contained as high as 14 per cent of nitrogen (equal to 17 per cent of ammonia), and of phosphoric acid 12 to 14 per cent (equal to 26 to 28 per cent of phosphate of lime). It, however, gradually deteriorated in quality as the deposits became worked out, the percentage of nitrogen becoming year by year less, until latterly Peruvian guano, as imported, contains only from 3 to 4 per cent of nitrogen (equal to 4 to 5 per cent of ammonia). This guano is, however, richer in phosphates, containing often 50 to 60 per cent of phosphate of lime, and 3 to 4 per cent of potash.[192]
(b) Other Nitrogenous Guanos.
The guanos, other than those which come from Peru, are chiefly purely phosphatic guanos, so that the term Peruvian has not unfrequently in the past been used as a generic term synonymous with the term nitrogenous, and consequently applied to all nitrogenous guanos independent of their source. There are, however, a few deposits other than the Peruvian which have yielded considerable quantities of valuable nitrogenous guano. Of those, the richest in quality—in fact, the richest of any deposits hitherto discovered—was the Angamos guano, which came from a rocky promontory on the coast of Bolivia. The few samples of this which have been analysed showed over 20 per cent of nitrogen. Unfortunately, the deposit proved to be comparatively insignificant in amount, and has long been exhausted.
Poorer in quality, but more abundant in quantity, were the deposits found on the Ichaboe and other islands off the south-west coast of Africa. These deposits were discovered shortly after the introduction of Peruvian guano, and for a few years supplied considerable quantities of valuable manure. The deposits first discovered were soon exhausted, so that for a number of years Ichaboe guano ceased to be procurable. Fresh deposits, however, were subsequently found, and considerable quantities have of late years been used in agriculture.[193] Ichaboe guano is inferior in value to Peruvian. It exemplifies the influence of small quantities of rain on guano deposits in impoverishing them in their nitrogen. In much of the Ichaboe guano imported into this country a large amount of feathers is found. It also contains an abnormally large quantity of insoluble matter.