REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 125 



melts easily, gives off no obnoxious fumes and is easily removed 

 from the ingots. In practice it is the custom to use about 5 

 pounds of the plaster to every 100 pounds of brass. 



Portland cement 



A certain part of the plaster of paris made in this country is 

 used in the manufacture of Portland cement. This use is legitimate 

 up to 2fc, but above that point it acts as a diluent, and the practice 

 is to be condemned. The effect of plaster of paris on Portland 

 cement is shown in the following, quoted from bulletin 44, New 

 York State Museum. 



The raw^ materials used in the manufacture of Portland cement 

 may sometimes contain sulfate of lime in the form of the mineral 

 gypsum, or sulfur may be present in the form of pyrite, which in 

 burning tends to react with some of the carbonate of lime, 

 yielding calcium sulfate. A similar effect may be caused if there 

 is much sulfur in the fuel used. The effect of this sulfate of lime, 

 if it does not exceed 2^ or Zi, is to greatly delay the setting of 

 the cement and also increase its final strength somewhat. If 

 present to the extent of 4^ or 5^, however, both these qualities 

 disappear, since formation of calcic sulfid is brought about, which 

 in turn reacts with the iron compounds in the cement and tends 

 to disintegrate it. The effect of sulfate of lime is shown in the 

 accompanying table, taken from Professor Johnson's work, 

 Materials of Construction^ p. 187. 



The German association of Portland cement manufacturers has 

 declared against any addition except up to the 2fc CaS04 to regu- 

 late setting time. It is the general practice in the United States 

 now to put in 2^i CaS04 to produce slow set. 



The following experiments are quoted by Lewis, showing the 

 effect of sulfate of lime on the rate of setting. 





ONE SORT OF CEMENT 



SETTING 

 TIME 



h. m. 



NEAT-CEMENT 

 BRIQUET 



BRIQ. 1 CEMENT, 

 3 SAND 



No. 



00 



§S 



405 

 456 

 508 

 543 



450 



518 

 572 

 568 

 688 



550 



1 



620 

 623 

 695 



718 



592 



1 



r-( 



too" 



650 



780 

 805 



618 



1 



t~ 



115 

 142 

 159 

 180 



168 



1 



13 

 §5 



168 

 212 

 238 

 263 



218 



m 



238 

 339 

 311 

 305 



318 



w 



302 

 353 

 368 

 375 



360 



1-1 



1 



As manufactured 







3 



10 



14 



10 



20 



30 











30 



323 

 315 

 375 

 423 



318 



360 



2 



Same w. .5 gypsum 



3^0 



8 



1 gypsum 



384 



4 



2 gypsum 



410 



5 



No gyp. but kept in store for 

 some months 



431 









