624 EXPERIMENT STATION RECORD. 



p. 594). — The effectiveness of different kinds of Thomas slag was very- 

 variable, ranging from 57.8 to 95.G per cent of that of a like anionnt of 

 water-soluble j^hosphoric acid. JN^o relation could be traced between 

 the percentage of phosphoric acid present and its effectiveness. The 

 different slags were digested in Wagner's acid ammonium citrate, and 

 quite close, though not absolute agreement was observed between the 

 solubility in this reagent and the fertilizing value. It is claimed that 

 with proper precautions this method offers a reliable means of valuing 

 slags. 



It has been suggested that it is unnecessary to attempt to reduce the 

 slag to a uniformly fine meal, since the part whicli resists the grinding 

 is less effective than that which is readily pulverized. To investigate 

 this point the fine meal and coarse meal from the same lot of slag were 

 each reduced to the same fineness and tested in vegetation experiments 

 with a like effectiveness for the two kinds of meal, thus justifying the 

 attempt to reduce all the slag to a uniform degree of fineness. 



A "prepared phosphate meal" (fine ground, soft i)hosiihate) offered 

 as a substitute for Thomas slag was tested, with unfavorable results. 



The results obtained by the author indicate that bone meal is one of 

 the least effective phosphatic manures, and that where it has produced 

 a good effect the result has often been largely due to the nitrogen 

 which it contains. In order to improve the effectiveness of the phos- 

 phoric acid the author treated bone meal with an amount of suli^huric 

 acid just sufficient to transform the phosphoric acid into a condition 

 similar to i^recipitated phosphate. Experiments with this prepared 

 bone meal gave promising results. 



Can diflicultly soluble Thomas slag be transformed into read- 

 ily soluble? P. Wagner {Chem. Ztg., IS {1894), No. 79, pp. 1511, 

 1512). — There is a wide variation in the solubility of the phosphoric 

 acid in Thomas slag from diiferent sources. The investigations of the 

 author indicate that the higher the percentage of silicic acid the greater 

 the solubility of the phosphoric acid in citrate solution. Hoyermanii 

 has reached a similar conclusion.^ The latter found that by fusing 

 sand with the slag just from the furnace the solubility of the slag in 

 citrate solution was increased from 58 to 84 per cent, but he believes, 

 nevertheless, that the slag which is most active in the soil is that which 

 contains the minimum of silicic acid and the maximum of lime. The 

 author combats this view and summarizes his own conclusions as follows : 

 There are slags which show a solubility in citrate solution of nearly 100 

 per cent and which are but slightly inferior to superphosphates. The 

 slags of the market vary widely in respect to citrate solubility, ranging 

 from 100 per cent to as low as 40 per cent. Tlie fertilizing value varies 

 in an almost corresponding degree. The principal condition for a high 

 solubility is a certain proportion of silicic acid. 



' Beitrag znr Frage der Citratloslichkeit der Pliospliorsaure im Tliomasschlacken- 

 mehl, Hauuover, 1894. 



