506 



CEMENTS, LIMES, AND PLASTERS. 



error into which most experimenters fall is to assume that these con- 

 stants are quite accurately known. As a matter of fact, even the sim- 

 plest of them the heat of dissociation of lime carbonate is given a 

 variation of almost 50 per cent by different chemists of about equal 

 standing; while the heats of formation of the silicates, etc., are much 

 less certain constants. 



In reporting and discussing actual tests, or in reading the reports 

 of such tests, it must, therefore, be borne in mind that the assumptions 

 which are necessarily made are based, in large part, on determinations 

 of more than questionable accuracy. 



Two such tests have been recently published, by Richards and Car- 

 penter respectively, and are summarized below. 



Richards' tests. Prof. J. W. Richards tested a 60-foot rotary at 

 the Dexter Portland Cement Company plant, Nazareth, Pa. The cement 

 mixture and the resulting clinker are said to have had the following 

 compositions : 



Raw Mix. 



Clinker. 



Silica (SiO 2 ) 13.38 21.27 



Alumina (A1 2 O 3 ) \ R n . / 6.42 



Iron oxide (Fe 2 O 3 ) j \ 3. 18 



Lime (CaO) 41 .96 66.70 



Magnesia (MgO) 1 .53 2.43 



Carbon dioxide (CO 2 ) 34.65 



Water 0.43 



The clinker " analysis " must evidently have been calculated 

 from the raw mix, and not obtained by direct analysis. 



A proximate analysis of the kiln coal bituminous stack from Fair- 

 mount, W. Va. gave: 



Volatile matter 38 . 10 



Fixed carbon 53.24 



Ash 8.06 



Moisture . 60 



"The following ultimate composition of the coal was assumed from 

 average analyses of coal from that region of similar proximate com- 

 position. 



Carbon 73. 60 



Hydrogen 5 . 30 



Nitrogen 1 . 70 



Sulphur . 75 



Oxygen 10 .00 



Mcisture . 60 



Ash.. 8.05 



