from Washington Territory. 239 



from those which it would be advisable to use if the object 

 were to determine with the greatest possible accuracy the 

 constituents of a rock or of a mineral. Still they are accurate 

 enough to guarantee fair results, particularly as great pains 

 have been taken to maintain the utmost possible uniformity of 

 conditions. 



The hydrochloric acid which was used for the extraction had 

 the spec. grav. = 1-112. The digestions with this acid were 

 effected in all instances on a constant water-bath for five days ; 

 25 cc of acid to about 2'5 grm of mineral powder were used. For 

 the determination of the total phosphoric acid the finely 

 triturated powders were digested for two and a half days on 

 the constant water-bath with nitric acid (spec. grav. =1-25) and 

 the phosphoric acid in the extract after precipitation with 

 amnionic molybdate was weighed as magnesium-pyrophos- 

 phate. For the determination of the total alkalies the method 

 of J. Lawrence Smith was used Sulphuric acid was only 

 determined in the hydrochloric extracts. On account of the 

 insignificant quantities found, the determinations of this soil- 

 ingredient were not repeated in the analyses by fusion. Only 

 traces of manganese were found. The determination of the 

 halogens (F, CI) was omitted, as it had no particular value for 

 this comparative investigation. 



Attraction of the soil with cold hydrochloric acid. — It was 

 interesting to see how the soil would be acted upon by cold 

 hydrochloric acid. For this purpose 25 grams of the soil were 

 digested with 250 cc hydrochloric acid (sp. gr. 1-112) at the 

 ordinary temperature. It was found that the extract con- 

 tained : 



Si0 2 0-22 per cent. 



P 2 5 0-28 



S0 3 0-01 " 



K 2 0-17 



Na 2 0-05 " 



CaO 0-69 " 



MgO 0-58 " 



MnO — « 



FeO — 



Fe 2 3 5-61 



A1 2 3 2-42 



u 



10-03 " 



In "How Crops Feed,"* Professor Johnson mentions the re- 

 sults of a similar experiment by Grouven on a soil of Salz- 

 miinde. Grouven found that hot diluted acid dissolved five 



* Page 370. 



