310 ANNUAL REPORT 
15. The specific gravity is then obtained from the formula: 
Weight of Cement 
Specific GLAVIN siyyeniece WORE: 
16. The flask, during the operation, is kept immersed in water in 
a jar (A), in order to avoid variations in the bemperalute of the liquid. 
Duplicate results should agree to 0.01. 
IE SPARSE aoe une BE, 1//y 7 Meagan eae ay eae 
Fig. 78. Specific gravity apparatus, according to Le Chatelier. 
17. A convenient method for cleaning the apparatus is as follows: 
Vhe flask is inverted over a large vessel, preferably a glass jar, and 
shaken vertically until the liquid starts to flow freely; it is then held still 
in a vertical position until empty; the remaining traces of cement can 
be removed in a similar manner by pouring into the flask a small quantity 
of clean liquid and repeating the operation. 
18. More accurate determinations may be made with the pincom- 
eter. 
‘FINENESS. 
19, Significance.—It is generally accepted that the coarser particles 
in cement are practically inert, and it is only the extremely fine powder 
that possesses adhesive or cementing qualities. The more finely cement 
is pulverized, all other conditions being the same, the more sand it will 
carry and produce a mortar of a given strength. 
20. The degree of final pulverization which the cement received at 
the place of manufacture is ascertained by measuring the residue retained 
