CHEMISTRY, 4G3 



methods. The method projiosod by I'\ Xobbe' for testing- seeds of 

 grasses mid eoiiifers -was also adopted. 



M. Maercker reported the results of cooperative tests undertaken 

 with a view to determining- the sources of error in the citrate method. 

 The results of tests by 9 institutions on 5 different sami>les of Thomas 

 slag of the Wagner and Xaumann methods are reported. The latter 

 method is described as follows: Digest 100 cc. of the filtered citrate 

 solution obtained by the Wagner method in an l^rlenmeyer Jlask with 

 30 cc. of concentrated nitric acid over the imked flame until the bulk 

 is reduced to about 20 cc, add 25 cc. of concentrated sulphuric acid to 

 separate the silica and boil for 10 minutes, wash into a 2r)0 cc. flask, 

 fill to the mark, Alter, and use 100 cc. of the ftltrate for the subseciuent 

 test by the citrate method. 



The results reported show a better agreement than in previous years 

 and indicate that the Wagner method gives reliable results when care- 

 fully carried out. It appears also that the allowable 0.75 per cent of 

 variation agreed upon between the German Agricultural Society and 

 the Association of Thomas Slag ^Manufacturers may be considerably 

 reduced. While the Wagner method, using a rotary apparatus, gives 

 reliable results on Thomas slag, it is not considered applicable to other 

 forms of i^hosphate, such as steamed bone meal. The ]^aumann method 

 apparently gave good results also. 



At a meeting of the fertilizer section at Eisenach, Ai)ril 15, 1800, it 

 was decided that the citrate soluble phosphoric acid of superphos- 

 phates should be determined directly by the Petermann metliod ami 

 not by taking tlie sum of separate determinations of water-soluble and 

 citrate- soluble phosphoric acid. 



M. Maercker also presented a report on the advisal)ility of requiring 

 that Thomas slag be sold upon the guaranty of content of fine meal 

 and citrate-soluble phosphoric acid. He reviewed investigations tend- 

 ing to show that the citrate solubility of the phosphoric acid is a 

 measure of the fertilizing value of the phosplioric acid in the slag, and 

 that the finer the slag the greater its solubility. The results of experi- 

 ments were also reported, which indicated that not only the citrate 

 solubility but the fertilizing value of slag for oats and alfalfa increased 

 with the percentage of silicic acid which it contained. 



C. Miiller described a new form of rotary apparatus, wliich carries 

 8 digestion flasks and is driven by means of a weight and clock-work 

 arrangement. 



.M. Maercker presented a report faxoring the adoption of a uniform 

 system of charges for determining citrate soluble phosphoric acid in 

 Thomas slag; and a report on the determination of nitrogen in feeding- 

 stuffs by the Kjeldahl method, with special reference to the action of 

 the last convention regarding the time of digestion of organic sub- 

 stances and the use of a mixture of i)hosphoric acid and sulphuric acid. 



iLauflw. Vers. Stat., 45 (1804), pp. 390, 391 (E. S. K.. 7. p. 15). 



