VIII.] ADULTERATIONS OF GUANO 235 



Few fertilisers have been subjected to a greater 

 amount of sophistication and adulteration than has 

 Peruvian guano, but since the passing of the Fertilisers 

 and Feeding Stuffs Act, and the better organisation 

 of its sale from a single distributing centre, there 

 has been but little fraud. It should always be found 

 on receipt to be in the sealed bags of i^- cwt. in which 

 it is distributed, and, as with all manures of variable 

 composition, the guarantee should be checked by 

 analysis, so as to ensure the delivery has been made 

 from the specified cargo. Deliberate adulterations with 

 sand or dirt can generally be detected by the incinera- 

 tion of a sample, the incombustible residue should be 

 white, and show but few signs of red oxide of iron. 



A certain arnount of Peruvian guano is treated with 

 sulphuric acid, so as to convert the ammonium carbonate 

 into non-volatile ammonium sulphate, and also to render 

 a larger proportion of the phosphoric acid soluble. In 

 this way is obtained " dissolved Peruvian guano," which 

 is made to contain about 6 per cent of nitrogen and 10 

 per cent, of phosphoric acid, of which 9 per cent, is 

 soluble in water. The use of acid adds to the value 

 of the guano, and not only will it store and travel 

 with less risk of deterioration through volatilisation of 

 ammonium carbonate, but the increased solubility of the 

 phosphates present, and their consequent activity, makes 

 the whole a better balanced manure. 



Compared with the Peruvian, the other deposits of 

 guano which can be classed as nitrogenous are com- 

 paratively unimportant, and only those from Ichaboe 

 Island and Damaraland on the south-west coast of 

 Africa have of late been articles of commerce in this 

 country. 



The Damaraland deposits are apparently exhausted, 

 while shipments of Ichaboe guano only come inter- 



