112 Philippine Journal of Science 1919 



in the Tropics. The high humidity of the atmosphere renders 

 it difficult to weigh calcium oxide in an ordinary platinum cruci- 

 ble without absorption of moisture. Results obtained with the 

 method just described have been found to compare favorably 

 with those of the official method; consequently it was adopted 

 as standard for the present work. 



In making a calcimeter determination, the sample is treated 

 with hydrochloric acid (density, 1.125), and the calcium car- 

 bonate content is calculated from the volume of carbon dioxide 

 evolved. In some laboratories the amount of sample taken 

 is not kept constant, but tables are used which indicate the 

 weight that corresponds to the observed temperature and pres- 

 sure. When this amount is placed in the appparatus, no reduc- 

 tion of the observed volume to standard conditions is necessary. 

 However, this arrangement has certain disadvantages when 

 used in routine work. The continual changing of weights be- 

 comes tiresome and the average routine analyst is likely to make 

 mistakes, especially at night. Also, if for any reason it is de- 

 sired to make a number of determinations at one time, the 

 samples cannot all be weighed at once because the temperature 

 or the pressure may change before the work has been com- 

 pleted and thus render the results incorrect. Also, if the ap- 

 paratus was standardized at a given temperature and pressure 

 with Iceland spar, the result could not be applied to a determi- 

 nation made after these conditions had changed without giving 

 rise to error. 



The method used in connection with this work has proved 

 more satisfactory. A standard raw mixture is prepared, having 

 as nearly as possible the ideal composition of the regular mixture. 

 This is prepared in quantities sufficient to last for a month or 

 two and is analyzed in triplicate for calcium by the potassium 

 permanganate titration method. At the beginning of his day's 

 work the analyst records the temperature and pressure, weighs 

 out an equal amount of the standard and of his first sample to 

 be tested, and places them successively in the calcimeter. As 

 long as the temperature and the pressure remain the same, it 

 is not necessary to use another portion of the standard ; but, if 

 either changes, a new standard must be weighed and analyzed 

 with the next routine sample. If during the course of the day 

 they both return to former values, the result of the standard 

 at that temperature and pressure may be used. 



Since with each determination conditions are the same for 

 both standard and sample, the calcium carbonate content of the 



