This section is from the book "An Elementary Outline Of Mechanical Processes", by G. W. Danforth. Also available from Amazon: An elementary outline of mechanical processes.
In any natural materials chosen for the manufacture of this cement, there must be ascertained:
(1) The proportions of the required ingredients contained.
(2) The kinds and quantities of other ingredients, which may be harmful in quantity or because of their chemical action.
 
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