208 § 109. ANALYSIS OF SOILS AND HOCKS. 



mechanical analysis, we hAve left the amount of fine sand 

 arid clay. 



Treat this residue in the same manner as directed in 

 § § 102 and 103 for the treatment of the corresponding 

 part of the soil. 



e. A determination of humus is generally unnecessary, 

 but if desired, can be conducted as directed in § 104. 



f. A determination of nitrogen will rarely be needed, 

 but may be made in the usual manner, with 5-10 grms. 

 of the marl. 



g. Some marls, particularly such as are rich in clay, and 

 contain but little sand, are much more efiective after hav- 

 ing been gently ignited. To test the marl in this respect, 

 heat it to a low red heat in a muffle, with free access of 

 Mr, and then make an aqueous extract of the ignited mass 

 by treating 500 grms. ot it with 2000 c.c. of distilled 

 water, with frequent agitation during a cold digestion of 

 48 hours. Then filter off * 1^ of the solution, or 1600 c.c, 

 for the determination of the alkalies ; evaporate this solu- 

 tion to dryness, eliminate silica in the usual manner, and 

 estimate the alkalies in the filtrate from the silica 

 (§ 93, G.). 



Another portion of 100 grms. of the ignited marl may 

 be treated with 800 c.c. of concentrated hydrochloric acid 

 in the cold, in the manner already directed, to estimate 

 phosphoric acid, and, if desired, the alkalies again. 



A. Analyses of the green sand marl of New Jersey. 

 (Cook.) 



Carbonic acid 2 



Lime 2.4 1.0 



Ma<?nesi:x .....0.4 2.0 



Ferric oxide 8.3 21.3 



Alumina 6.1 8.0 



Potasli 2.5 7.1 



Sulplmric acid 0.9 0.4 



Pliosplioric acid 1.4 1.3 



Silica [soluble] 20.2 45.9 



Silica [insoluble sand] 49.9 4.0 



Water 7.1 8.1 



99.4 99.1 



/ 



