ADULTERATION OF PHOSPHATIC SLAGS 219 



more the precipitate is separated by filtration and washed with 96 

 per cent, alcohol until the washings show no acid reaction with 

 methyl orange. The calcium sulfate precipitated is dried to con- 

 stant weight. This method gives a pure precipitate of calcium 

 sulfate, containing only traces of manganese. 



192. Estimation of Caustic Lime. The lime mechanically 

 present in basic slags is likely to be found as oxid or hydroxid, 

 especiajly when the sample is of recent manufacture. In the form 

 of oxid the lime may be determined by solution in sugar. In this 

 process one gram of the fine slag meal is shaken for some time 

 with a solution of sugar, as suggested by Stone and Scheuch. 73 

 The dissolved lime may be titrated directly with standard hydro- 

 chloric acid, or the lime is separated as oxalate from the hydro- 

 chloric acid solution by treatment of the solution with ammonium 

 oxalate. The calcium oxalate may be determined by ignition in 

 the usual way or volumetrically by solution in sulfuric acid and 

 titration of the free oxalic acid with potassium permanganate 

 solutions. The standard solution of permanganate should be of 

 such a strength as to have one cubic centimeter equivalent to 

 about o.oi gram of iron. The iron value of the permanganate 

 used multiplied by 0.5 will give the quantity of calcium oxid 

 found. 



193. Detection of Adulteration of Phosphatic Slags. The high 

 agricultural value of phosphatic slags has led to their adultera- 

 tion and even to the substitution of other bodies. Several patents 

 have also been granted for the manufacture of artificial slags of 

 a value said to be an approximation to that of the by-products 

 of the basic pig iron process. 



(i) Method of Blum. One of the earliest methods of exam- 

 ining basic slag for adulterations is the method of Blum. 7 * This 

 method rests upon the principle of the determination of the car- 

 bon dioxid in the sample. The basic phosphatic slag is supposed 

 to contain no carbon dioxid. This is true only in case it is 

 freshly prepared. The tetrabasic phosphate, after being kept 

 for some time, gradually absorbs carbon dioxid from the air. As 

 high as 19 per cent, of carbon dioxid have been found in slags 



" Journal of the American Chemical Society, 1894, 16 : 721. 



74 Zeitschrift fur analytische Chemie, 1890, '29 : 408. 



