I9I2] 



Fred J. Seaver and Ernest D. Clark 



421 



This was the extent of our knowledge when we began the present 

 study. Our first experiments were performed upon 200 c.c. of 

 heated soil extract containing about 0.3 per cent. of total soluble 

 matter, Its color was deep brown, its acidity was marked and it 

 had an odor of burned sugar. To this bot extract an excess of 

 basic lead acetate Solution was added; this caused a heavy brown 

 precipitate, which was filtered off and washed. Thedarkprecipitate 

 was suspended in distilled water and treatedwithhydrogen sulfid gas 

 for the removal of the lead. The lead sulfid thus formed was 

 filtered off and the clear brown filtrate was boiled to expel the excess 

 of hydrogen sulfid. The filtrate after the removal of the first lead 

 precipitate was yellowish and it, too, was saturated with hydrogen 

 sulfid to remove the excess of lead. The lead sulfid was removed 

 by filtration. The two Solutions now free from both lead and hy- 

 drogen sulfid were then subjected to the tests indicated below: 



The Solution of the material precipitated by basic lead acetate 

 deposited a crystalline powder upon spontaneous evaporation to 

 dryness. These crystals were insoluble in 95 per cent. alcohol, 

 which dissolved the brownish coloring matter mixed with them. 

 This treatment might afford a means of separating these substances. 

 Dialysis through collodion membranes did not produce any separa- 

 tions in any of our chemical work upon any of the various soil 

 extracts. 



We next obtained a large volume of heated soil extract (2.25 1.) 

 and added to it normal lead acetate Solution until no more precipi- 

 tate was produced. This precipitate was filtered off and hasic lead 

 acetate Solution added to the filtrate until no further effect was pro- 

 duced. In this case the addition of the basic salt caused a precipi- 



