APPENDIX. 



METHODS OF CHEMICAL ANALYSIS ESPECIALLY ADAPTED TO 

 THE RAPID EXAMINATION AND CLASSIFICATION OF ROAD 

 MATERIALS. 



I. COMPLETE ANALYSIS. 



A. Kiihxttuiri-K initiii/if insoluble in l<i/<lr<>cfi/<,ric nc'nl. 



The sample lor analysis is powdered on the agate mortar until all indication of 

 gritty particles has disappeared. The sample is then spread in a thin layer between 

 filter papers and allowed to stand overnight to air dry. 



Exactly 1 grain is weighed into a large platinum crucible and mixed with from 1 

 to 6 grams of a fusing mixture, which is made by grinding together in a porcelain 

 mortar 50 grams sodic carbonate, 50 grams potassic carbonate, and 2 grams of potas- 

 sic nitrate. 



The crucible is heated up gradually over an ordinary Bunsen flame until all bub- 

 bling has ceased and the contents are in a state of quiet fusion, when the blast lamp 

 is applied at its maximum temperature for ten minutes. The liquid fusion is imme- 

 diately poured into a platinum dish floating in a basin of water. The material still 

 adhering to the crucible is dissolved in dilute hydrochloric acid with the usual pre- 

 cautions, and after the removal of the crucible and cover the fused button is added. 

 After solution is complete the cover is removed from the casserole and the contents 

 evaporated to dryness as quickly as possible on the steam bath. As dryness is 

 approached the lumps are broken up with a button-ended stirring rod, and the heat- 

 ing continued until the residue has the consistency of a dry powder. This residue is 

 taken up with dilute hydrochloric acid and the silica filtered and washed. The 

 procedure at this point depends upon the degree of accuracy desired, and two meth- 

 ods are accordingly suggested. 



(1) Amirtttf iiu'thnd. The filtrate from the silica is again evaporated to complete 

 dryness, taken up with dilute hydrochloric acid, and the small amount of silica 

 filtered out, washed, and united with that obtained by the first filtration. Aft-r 

 burning off the paper the white silica is blasted at the highest temperature of tin- 

 blast lamp for fifteen minutes, cooled, and weighed. It is then treated with an excess 

 of hydrofluoric acid and two or three drops of strong sulphuric acid, evaporated 

 carefully to dryness, and finally blasted. The true per cent of silica present is shown 

 by the loss in weight. The weighed crucible containing the small residue is pre- 

 served for the ignition later on of the main portion of the alumina, together with the 

 oxids of iron, phosphorus, and titanium, but as the filtrate is divided into aliquot 

 parts, only one-fifth of the weight of the residue applies as a correction. 



(2) linfilif iijtjii'n.i -limit,- intthod. One evaporation to complete dry ness on the water 

 bath is made, care being taken to break up the lumps of the residue by stirring and 

 robbing with a flat-end glass rod as the point of dryness is approached. The rc.-idue, 

 which should be quite dry and powdery, is taken up with hydrochloric acid and the 



47 



