232 § 118. FE UTILIZE US. 



insoluble substance, diy it, boil it repeatedly with sodic 

 carbonate, to dissolve out the silicic acid (§ 58, a, 2), and 

 treat this insoluble residue with 6-8 times its wefght of 

 sulphuric acid to decompose the clay, as directed under 

 soil analysis (§ 102). Evaporate the solution in hydro- 

 chloric acid obtained above to dryness, and eliminate and 

 weigh the silica (§ 58, a, 1), and examine the filtrate from 

 the silica, as directed in Scheme I., except that manganese 

 need not be determined, unless a qualitative test reveals 

 its presence in notable quantity. 



GUANO. 



118. A. Peruvian cr other ammojiiacal guanos. — 

 Pulverize 200-500 grms. until the whole will pass through 

 a tolerably fine sieve. 



a. Water. — Estimate this in 1-2 grms. in such a manner 

 as to collect tlie ammonia that is expelled at the same 

 time by the heat (§ 90, d). The amount of ammonia, 

 given off is usually from 1-2° |^ of the weight of the guano. 



h. Non-volatile matters. — Ignite 6-8 grms. carefully in 

 a platinum crucible (§ 91). 



c. Nitrogen. — Burn 0.5 grm. with soda-lime. The mix- 

 ture should be made as quickly as possible in the tube, 

 and the bulbed tube attached immediately, to prevent any 

 loss of ammonia (§ 85, h). 



d. Actual ammonia. — Determine this in 1 grm. by 



Schlossing's process (§ 47, h). 



e. PllOSpllorlc acid, etc. — Digest the ash obtained in h 

 with nitric acid, filter out the sand^ wash, ignite, and 

 weigh it, and dilute the filtrate to 250 c.c. 



Determine phosphoric acid in 50 c.c. of this filtrate, by 

 t]i3 volumetric method (§ 115, a). 



For anotherinethod of estimating phosphoric acid alone, 

 mix 1 part of guano (1-2 grms.) with 1 part of sodic car- 



