114 



Philippine Jow^nal of Science 



1919 



Table I. — Atutlyses of raw materials. 



[Numbers give percentages.] 



Silicate. 



Lime- 

 atone. 



Loss on ignition -- 



Silica (SiCh) — - 



Iron oxide (Fe203) 



Aluminium oxide (AI2O3) . 



Calcium oxide (CaO) 



Magnesium oxide (MgO)._ 



Sodium oxide (Na20) 



Potassium oxide (K2O) _._ 

 Sulphuric anhydride (SO3) 



42.86 



5.77 



0.68 



53.76 



0.30 



6.84 



0.34 



22.88 



54.72 



5.41 



0.56 



1.88 



0.60 



1.65 



trace 



1.84 



trace 



trace 



3.24 



61.35 



4.82 



18.46 



5.22 



2.72 



2.26 



1.95 



trace 



On analyzing a number of samples by the four methods men- 

 tioned above and calculating all results to percentage calcium 

 carbonate, the agreement was not satisfactory. The analyses of 

 ten samples are shown in Table II. Most of these were prepared 

 in the laboratory from samples of the raw materials, dried and 

 ground to pass a 200-mesh sieve. These are only a few of many 

 comparative analyses that have been made from time to time. 



Table II. — The analyses of raw mix by several methods. 



[Numbers give percentages.] 



Sample No. 



By titration 

 with potas- 

 sium perman- 

 ganate. Total 

 calcium is cal- 

 culated to cal- 

 cium carbon- 

 ate. 



By calcimeter. By acid-alkali 

 Total carbon titration. Total 

 dioxide is cal- alkalinity is 

 culated to cal- calculated to 

 cium carbon- calcium car- 

 ate, bonate. 



Matter insolu- 

 ble in hydro- 

 chloric acid 

 with density 

 of 1.125. 



1 



2... 



3 



4 



5 



6 . 



7 



54. 40 

 62.30 

 66.50 

 76.80 

 77.80 

 78.00 

 79.60 

 83.00 

 84.40 

 86.50 



51.25 

 59.42 

 64.00 

 76.00 

 77.25 

 77.00 

 78.63 

 83.08 

 84.17 

 86.00 



53.03 

 61.31 

 65.35 

 76.26 

 76.30 

 76.30 

 78.88 

 81.71 

 83.22 

 85.14 



22.30 

 17.25 

 16.10 



11.20 : 



21. 68 | 

 21.82 

 11.04 j 



8.10 



7.00 



6.70 



8 . 



9 



10 . 





CAUSES OF ERROR 



In any analytical procedure certain errors of the process it- 

 self — such as inexact calibration of apparatus, slight solubility 

 of precipitates, difficulty of complete washing, and the like — can- 



