202 ANNUAL REPORT 
The two methods of separation appeared to check very well. However, 
his ingenious and elegant method is open to the objection that neither 
the water of hydration of the hydrosilicates nor the water of the cal- 
cium hydrate has a definite expulsion temperature. In fact, laborious ex- 
periments made by the writer for the Ohio Geological Survey have 
shown that it is impossible to distinguish with any degree of accuracy 
any particular stage in the dehydration curve. It also requires red heat 
to expel all of the water of hydration. 
The Earlier Work of Richardson.—In 1902 Dr. Clifford Richard- 
son, an American investigator, prepared the tri-calcium silicate synthetic- 
ally by fusion in the oxy-hydrogen flame, as well as non-dusting dicalcium 
silicates, both hardening in moist air and water. By means of micro-pho- 
tographs, he illustrated the crystalline character of Portland cement, and 
makes the statement that it is a solid solution. This claim has been made 
by numerous investigators for the last ten years or more, but none of them 
have, as yet, produced satisfactory physical-chemical data for the purpose 
of proving this hypothesis beyond all doubt, though at present it would 
not seem a difficult matter to study the melting points and cooling curves 
by means of the electric furnace and the optical pyrometer. ‘There is 
every reason to believe that all slags and slag like materials are solu- 
tions, and the work of Howe, Akerman,’ Vogt,? Hofman,? Ashley;* has 
furnished important contributory evidence, but we have as yet no right to 
say that Portland cement is a solid solution, just as the same thing has 
not been proven for slag and glasses. As has been said, a thorough survey 
of all the physical properties of pure Portland cements must be made with 
reference to the specific volume, heat of formation and other physical data 
made mention of elsewhere. 
The Work of Passow.—Dr. Passow, in 1903, examined Port- 
land cement clinker microscopically, and found essentially two predomi- 
nating constituents, a white crystalline mass, alite, and a dark ground 
mass or magma. ‘These two constituents are the hydraulic bodies of 
Portland cement. If, however, a third crystalline substance appears 
which is characterized by distinct striations, similar to those shown by 
plagioclase under the microscope, the hydraulicity is impaired in the 
proportion in which this matter, felite, appears. According to Passow, 
this offers a ready means of judging the quality of Portland cements, 
enabling one to detect cements too high in clayey matter; that is, cements 
approaching too closely the bisilicates. : 
.——————— 
1Stahl und Hisen, 1890, p. 424. 
* Betraege zur Kenntniss der Mineralbilding in Schmelzmassen, Christiania, 1892. 
°Transactions Amer. Inst. Min. Hng. Vol. 29, p. 682. - 
4Tbid, Vol. 31, p. 854. 
