PHYSICS, CHEMISTRY AND ENGINEERING 



163 



process in such a way that at any future time a similar batch 

 could be calcined and results of any of the tests checked or 

 carried out more in detail. However, no attention was paid 

 to selecting the strongest gypsum, and in order that a com- 

 parison might be possible betwen this and the company's 

 regular practice, test specimens were made from samples of 

 second settle gypsum taken from five mills of the United 

 States Gypsum Company. 



3000 



O .02 .04 .06 .OS -/O .12 .14- .16 .16 



F&rcenfcg'e of Reformer 



Fi#.6 



The strengths of these specimens are given in Table 1, in 

 which Gypsum No. 1 represents the specially calcined gypsum 

 from which all the specimens previously discussed were made. 

 These materials represent a geographical distribution cover- 

 ing five states and show a satisfactory uniformity in strength. 

 In all these specimens 0.1 per cent retarder was used. The 

 specimens were dried at 100° F and were tested at an age of 

 four days. 



