703 WBW TOME mate IH78EUK 



the quality of the manufactured product These changes are 

 three in number, i. c. driving off of the mechanically combined 

 water: driving oil the carbonic acid; fusing together of the Bilica, 

 alumina, lime ami iron. Each of these requirea a different tem- 



implishment, bu1 the attainment of the proper 

 to produce the last change La the most important 

 H the required temperature is overstepped, the cement is over- 

 burned and has little or no Betting power. 



Specific gravity. The specific gravity of the Portland cement 

 q an indication of the thoroughness of the burning, and is 

 ainable by Borne form of pyenometer. 



consists of a flask with a stopper, and having a long 

 graduated neck. The vessel is filled with benzin or turpentine 

 up to the zero graduation on the tube. A given weight of ce- 

 ropped into the tube, care being taken to allow all the 

 air bubbles to escape, when the rise of the liquid in the tube 

 indicates the volume of cement added. If metric units have been 

 d, then the Bpecific gravity of the cement is equal to the weight 

 of the quantity added in grams divided by the increase in volume 

 in cubic centimeters. 



Well burned Portland cement has a specific gravity of more 

 than 3.05, but should not exceed 3.15 or 3.20. 



In making this test it is necessary to see that there are no 

 lumps, and that the cement is thoroughly dried. 



Kilns. The typos of kilns used in the United States are: 

 intermittent or dome kilns; continuous kilns, of Dietzsch or 

 type; rotary furnace. 



In the old-fashioned intermittent kiln the bricks of cement and 

 soke are charged in alternate layers. The Dietzsch and Shofer 

 kali atinuous, as already Btated, and possess the great 



advantages of cheaper fuel, economy of labor, and of burning 

 the dry, poWdered material The rotary furnace effects an enor- 

 m< - of time and labor, and it is claimed that the tem- 



per can be regulated far more exactly than is possible in 



