PROPERTIES OF PORTLAND CEMENT. 371 



in the testing machine. The rate at which this disruptive strain increases in 

 different samples under various conditions of burning, grinding, and testing is 

 the kernel of the nut which we ought to crack before placing too much reliance on 

 values deduced simply from analyses or percentage of gain." 



Heretofore, it has been impossible to make other than a very limited study 

 of free lime in Portland cement. The few reliable methods iri for its detection 

 and estimation were so difficult and tedious as to be impracticable for general 

 application. They also failed to reveal the physical characteristics of lime so 

 detected. 



However, Alfred H. White 10 has recently described a quick, delicate, and 

 reliable method for the detection of free lime, the development of which promises 

 to be valuable. Unfortunately, this method has not yet been made quantitative, 

 but its application enables us to determine the relative amounts of calcium oxide 

 present and to distinguish between that which is sintered, nonsintered, or hydrated. 

 White has not had time nor opportunity to develop all of the possibilities of his 

 discovery; and those deductions which he has made from the application of this 

 test on commercial Portland cements have proved faulty in some cases because of 

 his assumption of a somewhat universal misconception, that "cements which pass 

 a perfect boiling test may safely be assumed to contain no free lime" 17 and because 

 the phenomenon of the formation and development of his so-called calcium phe- 

 nolate crystals was not sufficiently understood. 



This laboratory has employed White's test in the study of the cements 

 which have come to hand and as a consequence it has acquired a funda- 

 mental importance in our interpretation of the causes of man3 r otherwise 

 inexplicable phenomena. The proofs of the presence and the effect of 

 free and hydrated lime in commercial cements are so conclusive that a 

 somewhat extensive account of our investigations in this respect is 

 necessary. 



CALCIUM HYDROXIDE-PHENOL. 



Correctly to interpret the significance of the crystals described by 

 White and termed by him "crystalline calcium phenolate," we investigated 

 their formation, habit, and composition. 



Phenol will not react with calcium oxide or with calcium hydroxide 

 except in the presence of water. Calcium lrydroxide will combine with 

 phenol and water to form characteristic, long, slender crystals which are 

 extinguished by parallel and visible with crossed nicols. In an excess 

 of phenol, the length to which these crystals may grow depends upon 

 the amount of lime and water available at all stages of the reaction. By 

 carefully controlling these factors we have succeeded in obtaining crystals 

 2.0 millimeters long. However, water in excess of that capable of enter- 

 ing into the composition of the crystals destroys them, either by solution 

 or decomposition. 



The crystals formed from calcium oxide are in all respects similar to 



"Richter, W., Thonindustrie Ztg. (1903), 1863. This method only applicable 

 to fresh, dry clinker. Am. J own. Sci. (1906), 172, 266. 



16 Loc. cit. 



17 Loc. cit. 



