Note 140 — Chapter VI · Chemical and Mechanical Tests.
Reading edition
Geol. and Nat. Hist. Survey of Minn., XIX, Ann. Rept., p. 50. Thin sections of 2–3 sq. mm. area are of a convenient size, and they should be subjected to a red heat for (1½)-3 minutes. Too long a continuance of heat may render the sections too dark or lessen their transparency or produce melting.