374 



REIBLING AND REYES. 



FIG. 2.- 



-Characteristic crystals obtained by the micro- 

 scopic test from calcium hydroxide. 



tion of free lime, sintered, non-sintered and slaked, in Portland cement 

 and like materials. 



The amounts of oxide and 

 hydroxide used on the slide 

 were varied from a mere 

 trace to 3 milligrams; and 

 only those crystals were 

 compared which formed in 

 the thin sections under the 

 cover glass where the par- 

 ticles were well distributed. 

 The reasons for so doing are 

 obvious. The cover glass on 

 the slide keeps the solution 

 motionless. Therefore, each 

 particle of oxide or hy- 

 .droxide is confined more or 

 less to that part of the 

 solution which is in contact 

 with it. Either substance 

 tends to dehydrate and de- 

 phenolate the surrounding 

 solution and thus to retard 

 or prevent the further 

 growth of the crystals. 

 This is shown by the fact 

 that in solutions containing 

 less than 1.6 per cent of 

 water, the average length 

 of crystals formed from 

 isolated particles is greater 

 than from those which are 

 massed together. 



Theoretically, we would 

 expect to find a radical 

 difference between the mi- 

 croscopic results obtained 

 from the treatment of the 

 oxide and the hydroxide 

 with the test solution 19 

 advocated by White and 

 in reality this is the case. 

 If we calculate from the 

 formula of the crystals it 

 is evident that one drop (50 milligrams) of White's solution would contain 

 enough water to react with 0.92 milligram of calcium hydroxide and 

 produce 3.59 milligram's of the crystals. On the other hand, one drop 



19 Five grams of phenol + 5 cubic centimeters of nitrobenzol -f- 1 drop (0.05 

 gram) of water. 



' • ' r 



FIG 



3. — Characteristic crystals obtained by the micro- 

 scopic test from calcium oxide. 



