————————+————————-———- Per cent| Number of |of F. Degrees Alcohol | Requiring by |SUBTRACTION Volume. | of one from | Percentage. ————————+——————-—————- 21 | 5·85 22 | 5·625 23 | 5·4 24 | 5·175 25 | 4·95 26 | 4·95 27 | 4·725 28 | 4·725 29 | 4·5 30 | 4·5 31 | 4·5 32 | 4·5 33 | 4·5 34 | 4·5 35 | 4·5 36 | 4·5 37 | 4·5 38 | 4·5 39 | 4·5 40 | 4·5 41 | 4·5 42 | 4·5 43 | 4·5 44 | 4·5 45 | 4·5 46 | 4·5 47 | 4·725 48 | 4·725 49 | 4·725 50 | 4·725 51 | 4·725 52 | 4·725 53 | 4·95 54 | 4·95 55 | 4·95 56 | 5·175 57 | 5·175 58 | 5·175 59 | 5·175 60 | 5·175 61 | 5·175 62 | 5·175 63 | 5·175 64 | 5·175 65 | 5·175 66 | 5·4 67 | 5·4 68 | 5·4 69 | 5·625 70 | 5·625 71 | 5·625 72 | 5·625 73 | 5·625 74 | 5·625 75 | 5·85 76 | 5·85 77 | 5·85 78 | 5·85 79 | 6·075 80 | 6·075 81 | 6·075 82 | 6·075 83 | 6·3 84 | 6·3 85 | 6·3 86 | 6·525 87 | 6·525 88 | 6·525 89 | 6·75 90 | 6·975 91 | 6·975 92 | 7·425 93 | 7·425 94 | 7·65 95 | 7·65 96 | 8·1 97 | 8·1 98 | 8·325 99 | 9·45 100 | 9·9 ————————+——————————-- EXPLANATION.—In this case, the same calculation is performed as directed under Table I., except that the correction is to be _deducted_ instead of added. Aside from the water present in it, commercial alcohol is never pure, but always contains small quantities, at times mere traces, of substances having a peculiar, sometimes pleasant, sometimes disagreeable, but invariably intense odor, which are known as fusel oils. The variety of fusel oil differs with the raw material from which the alcohol was made; there is a potato fusel oil (chemically amyl alcohol), a corn fusel oil, a beet fusel oil, wine fusel oil (œnanthic ether), etc. Fusel oils, being themselves odorous substances, exert an influence on the fragrance of the perfume; hence it is a general rule in perfumery to use only alcohol free from fusel oil; that is, such from which the fusel oil has been extracted as far as possible by means of fresh charcoal. So-called “Cologne Spirit” of the best quality is, as a rule, practically free from it.