576 CEMENTS, LIMES, AND PLASTERS. 



From inspection of the above table it will be seen that old Portlands 

 were very low-limed products. Some, in fact, were too low in lime to 

 be considered, at the present day, as falling in the Portland class. 



Composition of American Portland cements. Table 221, contain 

 ing a large series of analyses of American Portland cements, has been 

 compiled by the writer from various sources. About half of the 

 analyses contained in it have already been published in different 

 books and periodicals, while for the remainder the writer is indebted 

 to the chemists of the various plants. 



Standard Methods of Analysis. 



The following methods of analysis are those suggested by a com- 

 mittee of the New York section, Society of Chemical Industry, consist- 

 ing of W. F. Hillebrand and Clifford Richardson. For exact work it 

 is desirable that these methods be closely followed. They are not intended 

 for use in making the rapid determinations which are necessary for the 

 control of the mix when the plant is in operation. A method of rapid 

 analysis has recently been published by several members of the Lehigh 

 section, American Chemical Society, which is probably well adapted 

 for use in the Lehigh cement district; but it is doubtful if it is worth 

 while attempting to formulate standard methods for rapid analysis, 

 since the requirements vary so much at the different plants. 



Method Suggested for the Analysis of Limestones, Raw Mixtures 

 and Portland Cements.* 



Solution. One-half gram of the finely powdered substance is to 

 be weighed out and, if a limestone or unburned mixture, strongly ignited 

 in a covered platinum crucible over a strong blast for fifteen minutes, 

 or longer if the blast is not powerful enough to affect complete con- 

 version to a cement in this time. It is then transferred to an evapora- 

 ting dish, preferably of platinum for the sake of celerity in evapora- 

 tion, moistened with enough water to prevent lumping, and 5 to 10 c.c. 

 of strong HC1 added and digested, with the aid of gentle heat and agita- 

 tion until solution is completed. Solution may be aided by light pres- 

 sure with the flattened end of a glass rod.f The solution is then evapo- 

 rated to dryness, as far as this may be possible on the steam-bath. 



* Eng. News, 50, p. 60. Eng. Record, 48, p. 49. Cement, Sept., 1903. 



f If anything remains undecomposed it should be separated, fused with a 

 little Na 2 CO 3 , dissolved and added to the original solution. Of course, a small 

 amount of the separated non-gelatinous silica is not to be mistaken for undecom- 

 posed matter. 



