234: GUANO. 



from 60 to 80 per cent., and that which has been fraud- 

 ulently adulterated leaves still more. The ash of gen- 

 uine guano, whether of good or bad quality, is always 

 white or grayish ; a yellow or reddish color bespeaks 

 an admixture of clay or earth. Good guano, when 

 first heated, evolves white vapors, with a powerful 

 odor of ammonia. 



IV. A similar quantity of guano is mixed, in a dish, 

 with several times its volume of water ; heat is then 

 applied, and the mass thrown upon a small filter (pre- 

 viously dried in the water- bath and weighed) ; the 

 residue on the filter is washed with hot water till a 

 small portion of the washing- water is not rendered tur- 

 bid by adding chloride of calcium and ammonia. The 

 filter, with the washed guano, is then thoroughly dried 

 in a water-bath and weighed. The better the quality 

 of the specimen, the less insoluble residue will be 

 obtained. Gfood samples of guano leave from 40 to 45 

 per cent., those of bad quality as much as 70 or 80. 

 If the guano be adulterated with common salt or with 

 Glauber's salt, it will behave to this test like a genuine 

 specimen, but furnish a greater quantity of ash in Ex- 

 periment III. 



V. The guano under examination, may be treated 

 with moderately strong hydrochloric acid. Good guano 

 effervesces but slightly ; a specimen of guano adulte- 

 rated with chalk, would effervesce strongly, and would 

 leave a proportionally larger quantity of ash in Ex- 

 periment III. 



VI. The ash obtained in III. is dissolved in dilute 

 hydrochloric acid, which should give rise only to slight 

 effervescence, if the guano be unadulterated. The so- 

 lution is filtered from the residue, the latter washed, 

 dried, thoroughly burnt, together with the filter in a 

 weighed crucible, over the spirit-lamp, and weighed. 

 This insoluble residue, consisting partly of sand, 



