Care should be taken in handling these materials for during work on the hexenyl compounds the hands of the investigator became poisoned. No remedies appeared to help the itching and burning. The affected parts dried up within three weeks leaving a yellow scar which soon disappeared. Heptenyl DerivativesDiheptenylpyrogallol, (C7HiS)2C8H(OH)3.-This synthesis followed the procedure given for dihexenylpyrogallol (II). From 0.4 mole of pyrogallol and 0.8 mole of 1bromo-2-heptene there was obtained 100 g. of crude reaction product (soluble in benzene and not extracted by alkali) which gave rise to 10 cc. of distillate in a closed system at 200°( 0.001 mm. or less). This 10-cc. portion was

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In the evaillation of mall Y methods of test, t h e t \\'O usual cri tena-precision and aCCl!-racy-are inwmcient. Accuracy is only applica ble wh ere compari sons with a standard can be made. Pr ec i~ion, when interpreted as d egree of r ep roducibiltty, is ]Jot necessarily a measu r e of merit, becallse a me thod may be high ly reproducible merely because it is too crude to detect small variations.To obtain a quantitative measure of merit of test mothods, a no\y concept-se nsitivity-is introdueed. If lV is a measure of some property Q, and lIM its standard de\' iation, the sensitivity of lIf, denoled "' ;II, is defined by the relation "'u=(dM/dQ) / IIM. It follows from this definition that lhe ~cnsit.ivi l v of a test method mayor mal' not be constant fOl' all values of the properly Q. A slatislCcal t est of significance -is derived for the ratio of sensitivities of alternatiye methods of test. Unlike the standa rd deviation and the coefficient of variation, sensitivity is a lllC'aSllre of merit that IS invaria nt with respect lo any functional transformation of the mcasnI"emC' nt , and is therefore independent of the scale in which the measurement is expressed .

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