Tlie acid \vas tlilritccl to one-fifth its fornicr attwgtli or eight. hiinclretlis of oiie per cent. I now ndoptcd the foliowiiig way of opemtiiig: A convex cover was pl:ieetl oil :L water h t h , tlie water i i i \ v i i i c . I i was lieatcil to boiling; c.avli picbee of 1~:ip~'r as tlil)l)(!d w : i ~ laid O I I the ulil)('r ('on\-es stirfacc of tlie covcr; this clried i t i n about one iniiiiite; i n practice this will be f ' o i i ~ i c l :it1 e lleiit w:ty of iisiiig tile ] J i l l ) C r . '171~ stantlard paper dipped oticc n i i d dried sliowed the reaction, but iiot strongly; n second dippiiig and drying broaglit it out pel.fectly; n third trc,:itnient ~n:icle tlic reactioii still strongel.. \\'lien n 1Japel' colored by this weak acid was di;)ped a secori,l time the previous change of color was iiitlisceriiible iintil it 11;ttl drietl again. The acid was reduced t o four-hundredths of one per cent.; t l l c . papel. j u s t slio\vcd tlie reaction after one dipping aiid dryirig : ; I sec o n i1 t rea t men t dcv clop ed i t 1)r r fee t 1y l'lic acid wns nest i~cduceilto t w o hundretlths of oiie per c e l l t . strc.iigt11; t.lie reaction appeared after three to five ti'eatrnents b i c t very faint I y . . l l ~ ) u the t same results were obtained with sulpliuric acid of' C(JF r c > p~iicIirigstrengths. 1 t ~ ( ! r,ci.ics of euperirnents indicates pretty clorely the liniits o f scrisitiyciiess; drying tile l ~ p e~rn n i i u be t t6o strongly insisted I C ~ M J I I ; ill~1
