The Philosophical magazine; a journal of theoretical, experimental and applied physics . 3 0 816 210 211 6-60 41-8 5-30 65-2 655 354 114-3 114 0 2-55 156-0 157-3 1-98 191-0 192-6 1-40 241-0 243-3 With 5 grams MgSOi the values found are f=20id and(,= l?A-C>. r, ,3 MgS04. Temp. 10° C. Permanganate, y- Time,minutes. Time,calculated. 1034 0 8-19 31-1 31-4 i 7-60 42-3 i 6-51 65-7 66-1 ! 4-91 113-0 113-4 3-81 158-1 159-9 3-16 194-4 196-4 2-50 245-2 244-3 of Chemical Change. 451 Now since/varios inversely as the rate of change, by com-paring the above three values the ratios are found to be 11
The Philosophical magazine; a journal of theoretical, experimental and applied physics . 3 0 816 210 211 6-60 41-8 5-30 65-2 655 354 114-3 114 0 2-55 156-0 157-3 1-98 191-0 192-6 1-40 241-0 243-3 With 5 grams MgSOi the values found are f=20id and(,= l?A-C>. r, ,3 MgS04. Temp. 10° C. Permanganate, y- Time,minutes. Time,calculated. 1034 0 8-19 31-1 31-4 i 7-60 42-3 i 6-51 65-7 66-1 ! 4-91 113-0 113-4 3-81 158-1 159-9 3-16 194-4 196-4 2-50 245-2 244-3 of Chemical Change. 451 Now since/varios inversely as the rate of change, by com-paring the above three values the ratios are found to be 115-1 : 131-9 : 201-3=100 : 100 + 14-6 : 100 + 5x14-9; showing that the amount of oxidation that takes 100 minutesto be performed in the blank requires 114-6 minutes in thepresence of 1 gram MgS04, itl 174-9 minutes with 5 gramsof the salt; or that the retardation is proportional to thequantity of the salt added, and equal to about 14-7 per cent,per gram. These three experiments are shown graphically inthe figure. Curves showing Retardation produced by 1 and 5 grams 10^ Time, minutes. The following table contains th e values of/and // for 0(]ua-tion (5), the mean in each case of several exjieriments, when2 grams of the various sulplrites were em{)loyeil, the tempe-rature being in every case 10° C. 452 Dr. J. J. Hood on Retardation Table I. Salt, /. ff- Time to oxidize 2 grams. iron from y toy. Blank 115 8 i156-2 77-2105-0 100-0134-8 , K,SO, 155-9 104-4 134-G Na^SO^ 1554 J 104-2 134-2 , 155-3 103-4 134-1 MgSO, 148-7 992 128-4 ZnSO, 141-3 941 122-0 CdSO, 1321 : 88-2 114-0 The noteworthy points exhibited by these numbers arethat equal weights of the sulphates of ammonium, sodium,potassium, and lithium produce equal retardation-effects ofapproximately 17*2 percent per gram ; whereas the sulphatesof zinc, cadmium, and magnesium, metals usually groupedtogether in the same sense as the alkali ones, all producedifferent effects. If the percentage retardation p
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