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๐ SIMILAR VOLUMES
I n attetiiptiiig to discnt:ing!c tlic c1icinic:il aiid physical changcs which occur in inincrtil lubricating oils during use, one is early fiiccd with the difiiculty that little is known of their chemical structurc before use.--!yt e~?y,( thcrcforc, Qo visualize what is happening to tlic hfdrocnrbo
Cliciiiicnl niid physicnl tcsts, tlioiigli not ncccssnrily iiifnlliblc tcst,s :is i i i i iiidiciition of the 1ubricnt.ing propcrtics of nil oil, nre very licccssnrg for controlliug tlic quality of supplics. A fcw words will bc said nboiit tlie tcsts wliicli nrc most coirimcrcinlly iinportnnt, thcsc
contin~es, imwcvcr, thnt Noclfcr 110s produccd bands "by tliffnsing silver nitrntc into p w e [thc italics arc inincl xrlntin. Strata wcrc nlso produccd when gelatin gels w r c subjcctcd to tlic nction of tanning ngcnt,s." dctnnlly, n 1 0 ~l l ~r l ~ Iiimsclf says that hc uscd coninwr-cia1 gelatin,