. Transactions. 29) and increase , ( / R9o/ / MBl y / / / / Zshm / / / / / f^ y / \ / -? X. ^ *^—— 0 2 I : J - i > r hn. Fig. 39.—Amalgams from another low-silver alloy. Contraction FOLLOA^^D BY EXCESSr\E EXPANSION. of mercury-alloy ratio (Fig. 31); that is to say, reducing the size of thealloy particles faciHtates the amalgamation, a result that we might haveexpected in kind if not in degree. But curve R 66, after reaching itsminimum, takes a slight upward turn, suggesting that there may be stillanother maximum beyond the second minimum of our type expansioncurve R 180 of Fig. 27. ARTHUR W
. Transactions. 29) and increase , ( / R9o/ / MBl y / / / / Zshm / / / / / f^ y / \ / -? X. ^ *^—— 0 2 I : J - i > r hn. Fig. 39.—Amalgams from another low-silver alloy. Contraction FOLLOA^^D BY EXCESSr\E EXPANSION. of mercury-alloy ratio (Fig. 31); that is to say, reducing the size of thealloy particles faciHtates the amalgamation, a result that we might haveexpected in kind if not in degree. But curve R 66, after reaching itsminimum, takes a slight upward turn, suggesting that there may be stillanother maximum beyond the second minimum of our type expansioncurve R 180 of Fig. 27. ARTHUR W. GRAY 693 Extension of Typical Expansion Curve By progressively increasing the thoroughness of amalgamation,more and more of the early portions of the type curve are wiped the same time the rate of reaction is increased so that the character-istic features make their appearance sooner and stand out more promi-nently. Therefore, if the slight rise at the end of R 66 really indicates. 0 2 3 ?? 5 6 7 hrs. Fig. 40.—Amalgams from high-silver alloys. the approach of another maximum, and not a mere vagary of the appara-tus, more thorough amalgamation ought to emphasize this feature ofthe curve. Since the curves of Fig. 35 were obtained with a mercury-alloy ratio of only and a trituration time of only min., it waseasy to test the matter. Fig. 36 shows how R 59 and R 66 were thustransformed into R 62 and R 67 upon increasing the mercury-alloy t)94 METALL0C4RA1HIC PHENOMENA OBSERVED IN AMALGAMS ratio to and the mixing to 6 min. trituration with mortar and pestlefollowed by 10 min. kneading in the hand. Influence of Thermal Softening and of Re amalgamating aHardened Amalgam As a final example of transformations brought about by physicaltreatment of this same alloy, Fig. 37 is given. It shows results obtainedby heating a hardened amalgam until it softens {R 39), and by mixingmore mercury with fihngs from a hardened amalgam (R 40). RWO /^ / < / RI4I/ \
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
