147 



- / nf dilute and concentrated hydrochloric acid oyfoyriter.' 



While one of the results in the above table must be explained, the referee is con- 

 vinced from a number of tests made years since that neither dilute nor concentrated 

 hydrochloric acid ha- any appreciable effect on pyrites, and would therefore recom- 

 mend i In- u - of the corn-cm rutr<l acid in the solution of phosphate rock, heating for a 

 definite linn-. 



Of cour.-e, tin- u-e .)f sulphuric acid of 50 li. (which also has no action on pyrites), 

 followed b\ -illation in dilute hydrochloric acid, would more nearly approximate 

 actual condition-, and it iniirht be well if the next referee would investigate this method 

 of -olution as compared with simple solution in concentrated hydrochloric acid. 



RXAJONJ M (ITRATE FOR NEUTRALITY. 



B \\.i- IK decide whether the solutions were neutral or not, and as no 

 t\\o chem n the exact |Niint of neutrality, whether from lack of sensitiveness 



of the indicator.-. ..r olor-hlindne-s on the part of the operators, he decided to make 

 an analysis of each sample according to the method outlined in his last report to the 

 association, and he guided by iho.-e re-nits in deciding upon neutrality. The follow- 

 ing method nf anal\ -i~ \\a- ad. -pled: 



'r\\ent\-!ive cubic ccntiinci. r- of ,-ach solution was pipetted into a 250 cc flask, 

 made to mark, -hakeii. and _'.*> CC iipette.l into a distillation flask; to the solution in 

 the ila-k. in ' of fourth-normal caustic soda solution were added, and the contents of 

 the ila.-k distilled into -JO cc of half-normal acid, continuing the distillation until the 

 volume of i he di.-tillate measured from 65 to 70 cc. The ammonia in the distillate 

 was then titrated l\ mean- of tenth-normal alkali. The residue in the retort was 

 1 into an Brlemneyer tla-k. excess of standard acid added, then a few drops of 

 phenolphthalein, and the excess estimated by means of tenth-normal alkali. From 

 the icMilt the weight of citric acid originally combined with the ammonia was cal- 

 culated. Calculating fnun the formula of the pure salt, (NH 4 ) 3 C,jH 5 O 7 , that the ratio 

 of ammonia (Nil i" citric acid was as 1 to 3.765, a basis of comparison was established. 

 The re-nli- obtain. -d are giveo in the table below. As only three official chemists 

 sent their solution-, the anal\ -i- are designated by number and not by name. 



Dettrintnntmn f n< utrnlitij of ammonium citrate solutions. 



