148 



In this table all the solutions which showed materially more citric acid than 3.765 

 parts to 1 of ammonia also showed a decidedly acid reaction to coralliu. 



It appears that some chemists prepare their ammonium citrate solution by treating 

 the citric acid with excess of ammonia and then leave the hot solution to neutralize 

 itself, or finally adjust it, some by means of red and blue litmus paper, others by cor- 

 allin. Some state that they have never been successful in the use of corallin; others 

 adjust finally by means of the alcoholic solution of calcium chlorid. In the opinion 

 of the referee,-if a chemist has succeeded in getting his solution neutral or practically 

 so, he will almost certainly put it out of joint by attempting to make it exact with the 

 calcium chlorid solution. The referee finds that an alcoholic calcium chlorid solution 

 which is exactly neutral to corallin is acid to phenolphthalein, and alkaline to cochineal ; 

 that after the precipitation of the citric acid from 10 cc of the ammonium citrate solution 

 by 50 cc of the calcium chlorid solution, calcium citrate still remains in solution in the 

 filtrate, which may be proved by boiling some of the clear solution, when a precipitate 

 of calcium citrate will appear. The presence of this salt, in the opinion of the referee, 

 renders the use of cochineal as indicator unreliable. One of the solutions in the above 

 table, which is the most acid of all by analysis, was neutralized in this way. There 

 are materials (notably fertilizers containing bone) on which a slight difference in 

 neutrality of the ammonium citrate solution makes a great difference in the results. It 

 is a reproach to the association that it has suffered the matter to remain in its present 

 condition so long. While the referee has a strong personal conviction that the only 

 proper method of making the solution neutral is by analysis and calculation of the 

 exact quantity of ammonia or citric acid to be added to it, still he hesitates to urge it 

 officially, as no work has yet-been done by any other referee along this line, and because 

 the referee is himself no longer an official chemist. 



The referee desires to acknowledge the valuable aid and suggestions of Mr. J. Q. 

 Burton in all of this work and the analytical assistance of Mr. F. C. Atkinson. 



THOMAS SLAG. 

 By J. B. LINDSEY. 



Thomas slag or basic phosphatic slag is a by-product in the modern method of steel 

 manufacture from ores containing noticeable quantities of phosphorus. The process 

 of removing the phosphorus from the ore was discovered by the English engineers 

 Gilchrist and Thomas and, briefly stated, consists in adding to the so-called "con- 

 verter " containing the molten ore a definite quantity of freshly burned lime, which 

 after a powerful reaction is found to be united with the phosphorus and swims upon 

 the surface of the molten steel in the form of a slag. 



COMPOSITION. 



The composition of the Thomas or Belgian slag varies according to the character of 

 the ore and the success of the process for removing the impurities. The following 

 figures show such variations: a 



Per cent. 



Phosphoric acid 11-23 



Silicic acid 3-13 



Calcium oxid (lime) 38-59 



Ferrous and ferric oxids 6-25 



Protoxid of manganese 1- 6 



Alumina 0. 2- 3. 7 



Magnesia 2- 8 



Sulphur 0. 2- 1.4 



a Adolf Mayer, Agricultur Chemie, 6th ed., vol. 2, pt. 2, pp. 138-139. 



