152 



phoric acid in this material, however, by the Wagner method of analysis showed 

 only 1.029 per cent of available phosphoric acid or 6.13 per cent of the whole, while the 

 basic slag by this same method showed 15.48 per cent of available phosphoric acid or 

 87.4 per cent of the whole. The point in making mention of this apatite is to show 

 that in case the phosphatic slag is adulterated with material of this nature the mechan- 

 ical method of valuing the slag would prove decidedly misleading, and it is because 

 of this that the method of valuing the phosphoric acid in basic slag has become obsolete 

 in European countries. 



During the past year the writer has had experience with the Wagner method of 

 determining available phosphoric acid in basic slag and the valuations of this material 

 that appear in our fertilizer bulletin have been based on this method. 



The Wagner method as used in foreign Countries has shown results agreeing closely 

 with those obtained in field trials. It is as follows: 



Weigh 5 grams of the slag and transfer it to a half-liter, bottle-shaped flask containing 

 5 cc of alcohol to prevent the slag from adhering to the flask. Make up to the mark 

 with a 2 per cent citric acid solution at 17.5 C. The flask is fitted with a rubber 

 stopper and put at once into a rotary apparatus for thirty minutes, making thirty to 

 forty revolutions per minute. At the end of a half hour the solution is immediately 

 filtered and the phosphoric acid is determined in an aliquot part of the clear solution 

 by means of molybdic solution in the usual manner. 



The analysis of two samples of slag by this method at the Massachusetts experiment 

 station shows the following close agreement. No. 1, available phosphoric acid, 

 15.42 and 15.38; No. 2, 15.81 and 15.75. 



In case of a bona fide sample of basic slag the valuation based upon mechanical 

 analysis by use of a 100-mesh sieve agrees closely with the valuation based on the 

 availability of the phosphoric acid by the Wagner method. In case, however, of a 

 sample of slag adulterated with the natural mineral phosphate, the valuation based 

 on mechanical fineness is obviously open to severe criticism. I think this question 

 of sufficient importance to warrant a motion that I would herewith make, that the 

 referee on phosphoric acid be instructed to make a study of the Wagner method of 

 analysis with samples of basic slag and natural mineral phosphates, with a view to its 

 adoption as an official method for the determination of available phosphoric acid in 



The papers by Mr. Lindsey and Mr. Raskins relating to the valua- 

 tion of phosporic acid in basic slag were referred to Committee A for 

 action on recommendations contained therein. 



REPORT ON DAIRY PRODUCTS. 

 J. M. BARTLETT, Referee. 



According to instructions given by vote of the association last year the referee has 

 continued the study of analytical methods for condensed milks. The results reported 

 at the last meeting indicated that the analysis of the sweetened product presented 

 much greater difficulties than the unsweetened, particularly in the determination of 

 fat; therefore, the referee decided to confine the work to one brand only, the sweetened 

 milk. Twenty-six analysts signified a desire to cooperate, but not all of them were 

 official chemists, many being commercial chemists more or less directly interested in 

 food analysis. 



SAMPLES OP MILK. 



On about April 1, a can of sweetened condensed milk together with a copy of instruc- 

 tions was sent to each chemist requesting the same. It was first intended to get a 

 quantity of milk in bulk, thoroughly mix it in the laboratory, and send out the samples 



