water bath, else the alcohol will boil over. When the alcohol has 

 evaporated there will be left a large amount of ammonium chloride 

 in the residue. Care must be taken that all the alcohol is volatilized, 

 after which the residue is dissolved in about 30 or 40 c. c. of water. 

 T<> the solution add 2 or 3 c. c. of HNO ;{ ; cover and heat on the bath 

 very gradually (else there will be a violent ebullition due to the liber- 

 al i>n of nitrous oxide). When ebullition has subsided, remove the 

 cover and evaporate to dryness; then to the dish when cooled add 

 two or three drops of HNO a , 10 or 15 c. c. of water, and warm until 

 solution is effected. Wash from the dish with a minimum quantity 

 of water into a beaker of suitable size for the determination of P-( ).-,, 

 volumetrically. 



To this solution add about a teaspoonf ul of dry ammonium nitrate ; 

 let stand in a water bath at a temperature of about 50 C. ; add 10 or 



FIG. 3. Apparatus for preparing acidulated alcohol. 



1 .') c. c. of the ordinary molybdate solution, and let stand about thirty 

 minutes, \vith an occasional shaking. Decant through a 9 cm. filter; 

 wash the precipitate into the filter, and continue the washing until 

 live of acid, by test with phenolthalein or litmus. It generally 

 iv.juires about 200 c. c. of water for this washing. The filter and 

 its contents are returned to the beaker, and by the use of a stirring 

 md and a little water the paper is beaten into a pulp. The titration 

 is made in the usual way, with KOH and HC1, using phenolthalein 

 in indicator. In this laboratory the alkali used is one-half the 

 otHeial strength; that is, 100 c. c. neutralizes 16.19 c. c. of normal 

 acid. This makes 1 c. c.=.0005 gram P 8 O S . The weight of P < > 

 here found is to be divided by 1GO grams, and the result expressed in 

 parts per million, as was that for K 2 O. 



As will be seen, in this method the total weight of soil is used in 

 each determination instead of dividing the solution, as is generally 



