June, 1927
I ~ V D C S I ' R I A L..im ENGINEERISG! c f I t x I s ' r I z y
I h e present expansion hiis been due almost entirely t o recent improvemeiits in cells and eiect,rodes wbich have 61iidly been demonstrated to be coinniercially practicabie. >-em:.
Figure 18& Specific Condvctiviry
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Suear-Ash Bridee
In applying eieet,rornetric control to industry, it is at tiirics vcry difficult to predict rvlietlier a giveii problem is likely tiJ he solved by this mains. I t is likewise iihiiost impossible t o predict the corrcct rmge for a recorder or controller, without making prclirnin:iry measurements at l.he plant in which tlie coritrol is to be installed. Frequently it is advisable t o permit the operator to make preliminary measurements i n order to collect data for calibrating the final inst,rument. Wliile mnking these measurements lie gains ( knowledge and Inter no difficulty is experienced over t,o recording or control apparatus.
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Reeordiiig apparatus wliicli ea11 be applied to a large number of quite different problems has helped to solve this difficulty. Therecorder that uses areference cell, in w h i c h various solutions may he placed, is a good example of this adaptability. Even in using this instrument., however, the proper rmge must be employed in order t.o obtain the desired sensitivity. Instruments have also been made with variable rmges in nii at.ternpt to sdve these difficulbiea. \Vliile the arecedirig d e s c r i p t i o n iriclulied tlie most iinportaiit fields where elcctroinot.ric control is at preseiitcmployed i n inilust.ry, no attempt will be made to sinnin,zriae the possiMe uses to whiali ,siich cont,rol may be applied in the future. In all the cases cited tlrere are t i t least one or more installations in successful operation at tlie present tinie. I'resent aroeress is necessarily Figure 19 -11-IonReeord, with Tungeten Electrode. at fhe Muntebello Pilfers, slow. owing to the eamrnorp~ ~4~ ~~~~~, necessity for overcoming v,zrioiisohstacles, many of which are peculiar t,o particular installitions. Sfter more experience has been obtained along these lines, it is believed that the subsequent progress will be relatively rapid.
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Flames of Atomic Hydrogen','
T
HE lieu,t carried away from an incandescent wire by
a surrounding inert gas a t ordinary tcmperatures incre:rses roughly in proportioii to the 1.9th power of the absolute tcmperat,ure, T , of the filament.2 This relation liolds, for example, for such gases as nitrogen, argon, and mercury vapor up to t,lie teniporaturc of melting tungsten, :X
