12 VOELCKER OTi the Value of Artificial Manures. 



It will be observed that instead of 16 per cent, of ammonia 

 this " essence of guano " contained only 6-10ths per cent., and 

 instead of 20 per cent, of bone-earth only 2 and 3-10ths per cent. 

 To make up for this deficiency, no less than 34 per cent, of sand 

 and brickdust, 15 per cent, of gypsum, 8 per cent, of chalk, 

 and 15 per cent, of common salt, have been added. 



A more fraudulent case has scarcely ever come under our 

 notice. The exceedingly small amount of ammonia (not quite 

 7-iOths per cent.) shows that, if any, a mere trace of Peruvian 

 guano was incorporated in this worthless mixture, which, indeed, 

 when examined under the microscope, appeared to have been 

 compounded by mixing together gypsum, lime, sand, brick-dust, 

 common salt, and sheep's dung. So clumsily was the mixture 

 made that the last-mentioned ingredient could be readily identi- 

 fied by its characteristic globular form. 



Genuine Peruvian guano, we may observe, should contain 

 from 50 to 60 per cent, of organic matter, yielding at least 16 per 

 cent, of ammonia, 18 to 20 per cent, of bone-earth, 6 to 8 per 

 cent, of alkaline salts, and no more than 2 to 3 per cent, of in- 

 soluble silicious matter (sand). Genuine guano, on burning, 

 leaves a perfectly white ash, which does not effervesce with an 

 acid ; whilst adulterated guano generally produces, on burning, 

 a reddish-coloured ash, or a white ash, which either does not 

 readily dissolve in acid (showing the adulteration with gypsum), 

 or strongly effervesces with an acid (proving the adulteration with 

 chalk). 



But perhaps the easiest way to ascertain if Peruvian guano is 

 genuine or adulterated is to weigh a bushel. If pure, it will 

 weigh from 68 Ibs. to 72 Ibs. If much adulterated, considerably 

 more, no cheap material having been discovered with which 

 guano can be readily adulterated without increasing its specific 

 gravity. 



Nitrate of Soda. We are glad to mention that none of the 

 samples which we examined during the last season were in any 

 way adulterated. 



By far the most common adulteration in nitrate of soda is 

 common salt, the presence of which can be detected, if it is con- 

 tained in the nitrate in somewhat considerable quantities, by 

 throwing some of it on red-hot coal, when it will burn with a 

 green flame, whereas pure nitrate of soda burns with a bright 

 yellow flame. 



Soot. The efficacy and commercial value of soot mainly de- 

 pends on the amount of ammonia which it contains in combina- 

 tion with sulphuric acid. Commercial soot frequently is adul- 

 terated with finely-sifted coal-ashes ; different samples, moreover, 

 naturally contain variable quantities of ammonia. It is advisable, 



f 



