S T A S D A R D I Z I S ( + IITDROlIETERY.
STAKDARDIZIKG HYDROMETERS. By PROF.W, P. R h s o s . Some time since I prepared standard instruments, arranged for liqiiitls lighter tllitll water, for one of our large corporations. T h e hydrometers were constructed by C11:ts. ,J. Tagliabue ; the stems lrft unmarked and the tops open. Each instrument (there were four in a set) had a capacity of b u t .!O" 13aum; ; the four thus covering the scale from 10" to 90' B. IT1)oneach stem I detcrmined three points, upper, middle and I o w r . and fixed thereon the permanent paper markings. I n obtaining these points I employed Clarke's method, weighting t h e instrument internally and using water a t 60° F. as the floatingliquid. The papers having been placed and fastened the added weights were removed a n d the stems were then closed before t h e blowpipe. -4s n check, the closed hydrometers were next floated in prepared liquid (oils generally) a t GO" F., of specific gravities ezactly q t i a l t o t h e indications 011 t h e paper markings, arid the points wliere the liquids cut the stems noted by slight file scratches. K h a t is particularly worthy of attention is t h e lack of uniformity in the readings its determined by t h e two methods. Greater care could. not have been exercised than was given during the entire work, a n d I am forced to ascribe the variations in reading (not far from & of a degree) to differences of surface attraction in t h e several liquids. Such differences would naturally result in the mounting of liquids to unequal heights u p t h e stem of t h e hydrometer ; and, moreover, even granting t h a t t h e volume of liquid mounting t h e stem were constant, yet t h e varying specific gravity thereof would always enter as a disturbing factor of the total weight of t h e instrument. From my work in this matter I a m convinced that hydrometers should be standardized by floating in water alone, according to Clarke's method ; and I would further add t h a t I believe a degree of delicacy is often demanded of them beyond what their capabilities can bear. IIEXSSELAER P O L Y T E C H N I C IKSTITUTE,
Troy, K.Y., Aug. Sth, 1887.
