13 



concentration by evaporation. Exactly 125 cc of the clear liquid (one-half the total volume 

 of liquid) are placed in an Erlenmeyer flask, heated to boiling to expel traces of carbon 

 dioxid and to insure a sharp "end reaction," and then titrated with standard fixed alkali, 

 phenolphthalein being used as the indicator. 



Twentieth Convention, 19O3, Bui. 81, Cir. 13. 



Page 72, under "4 (a) Acid digestion of the soil," eleventh line, 

 for "and again evaporate to complete dryness" substitute the fol- 

 lowing: " filter, wash free of chlorids, and again evaporate to com- 

 plete dryness as before." 



Page 74, under "4 (g) Determination of phosphoric acid," mark 

 the official method (a) and insert the following: 



(b) Optional provisional method: Proceed as in (a) "until all the phosphoric acid is 

 precipitated," and then finish the determination as follows: 



After standing for three hours at a temperature not above 50, filter on a small filter, 

 wash with water until two fillings of the filter do not greatly diminish the color produced 

 with phenolphthalein by one drop of standard alkali. Place the filter and precipitate 

 in the beaker and dissolve in standard alkali, add a few drops of phenolphthalein solution 

 and titrate with standard acid, 1 cc of which equals 0.0005 gram of phosphoric acid (P 2 O 5 ). 



Page 74, "4 (h) Provisional method for determining available phos- 

 phoric acid," omit the word " available" from the heading. 



Page 76, under " 10. Determination of humus," tenth line, change 

 the sentence beginning "The supernatant liquid" to read as follows: 



The supernatant liquid is filtered, and the filtrate must be perfectly clear and free from 

 turbidity; evaporate an aliquot portion, dry at 100, and weigh. 



[The retiring referee was instructed to make necessary verbal 

 changes in the methods and submit them to the secretary for pub- 

 lication.] 



VII. METHODS FOB THE ANALYSIS OF ASHES. 

 Eighteenth. Convention, 1901, Bui. 67. 



Page 77, name of section is changed to "VII. Methods for the 

 Determination of Inorganic Plant Constituents." 



Page 79, insert as provisional the modified nitric acid method 

 for the determination of sulphur in plants: 



MODIFIED NITRIC-ACID METHOD FOR THE DETERMINATION OF SULPHUR IN PLANTS. 



Place 5 grams of material in a 3|-inch porcelain evaporating dish, add 20 cc of nitric 

 acid (cone.), and heat the mixture cautiously on a water bath until ail danger of overflowing 

 is passed. Partly evaporate, add 10 cc of a 5 per cent solution of potassium nitrate, evapo- 

 rate the mixture to complete dryness, and ignite, at first gently and then under a blast 

 lamp, until the residue is white. Then dissolve in hydrochloric acid, evaporate to dryness, 

 and heat for some time in an air bath to render silica insoluble. Take up the residue in 

 water, with the addition of a little acid, filter, and precipitate the sulphuric acid with 

 barium sulphate, etc., in the usual way. 



[This method was dropped in 1905.] 



