| March | 24. | pitched the | tun at | 51°: yeast 4 gallons. | ||
| Temp. | Gravity. | |||||
|---|---|---|---|---|---|---|
| 25. | 52° | 41 | pounds. | |||
| 28. | 56° | 39 | ||||
| 30. | 60° | 34 | ||||
| April | 1. | 62° | 32 | |||
| 4. | 65° | 29 | added 1 lb. of yeast. | |||
| 5. | 66° | 25 | ||||
| 6. | 67° | 23 | ||||
| 7. | 67° | 20 | ||||
| 8. | 66° | 18 | ||||
| 9. | 66° | 15 | ||||
| 10. | 64° | 14 | ·5 cleansed[7]. | |||
[7] Brewing (Society for diffusing Useful Knowledge), p. 156.
The following table shows the origin and the result of fermentation, in a number of practical experiments:—
The second column here does not represent, I believe, the solid extract, but the pasty extract obtained as the basis of Mr. Allen’s saccharometer, and therefore each of its numbers is somewhat too high. The last column, also, must be in some measure erroneous, on account of the quantity of alcohol dissipated during the process of fermentation. It must be likewise incorrect, because the density due to the saccharine matter will be partly counteracted, by the effect of the alcohol present in the fermented liquor. In fact, the attenuation does not correspond to the strength of the wort; being greatest in the third brewing, and smallest in the first. The quantity of yeast for the above ale brewings in the table was, upon an average, one gallon for 108 gallons; but it varied with its quality, and with the state of the weather, which, when warm, permits much less to be used with propriety.
The good quality of the malt, and the right management of the mashing, may be tested by the quantity of saccharine matter contained in the successively drawn worts. With this view, an aliquot portion of each of them should be evaporated by a safety-bath heat to a nearly concrete consistence, and then mixed with twice its volume of strong spirit of wine. The truly saccharine substance will be dissolved, while the starch and other matters will be separated; after which the proportions of each may be determined by filtration and evaporation. Or an equally correct, and much more expeditious, method of arriving at the same result would be, after agitating the viscid extract with the alcohol in a tall glass cylinder, to allow the insoluble fecula to subside, and then to determine the specific gravity of the supernatant liquid by a hydrometer. The additional density which the alcohol has acquired will indicate the quantity of malt sugar which it has received. The following table, constructed by me, at the request of Henry Warburton, Esq., M. P., chairman of the Molasses Committee of the House of Commons in 1830, will show the brewer the principle of this important inquiry. It exhibits the quantity in grains weight of sugar requisite to raise the specific gravity of a gallon of spirit of different densities to the gravity of water = 1·000.
| Specific Gravity of Spirit. | Grains, Weight of Sugar in the Gallon Imperial. |
|---|---|
| 0·995 | 0·980 |
| 0·990 | 1·890 |
| 0·985 | 2·800 |
| 0·980 | 3·710 |
| 0·975 | 4·690 |
| 0·970 | 5·600 |
| 0·965 | 6·650 |
| 0·960 | 7·070 |
| 0·955 | 8·400 |
| 0·950 | 9·310 |
The immediate purpose of this table was to show the effect of saccharine matter in disguising the presence or amount of alcohol in the weak feints of the distiller. But a similar table might easily be constructed, in which, taking a uniform quantity of alcohol of 0·825, for example, the quantity of sugar in any wort-extract would be shown by the increase of specific gravity which the alcohol received from agitation with a certain weight of the wort, inspissated to a nearly solid consistence by a safety-pan, made on the principle of my patent sugar-pan. (See [Sugar].) Thus, the normal quantities being 1000 grain measures of alcohol, and 100 grains by weight of inspissated mash-extract, the hydrometer would at once indicate, by help of the table, first, the quantity per cent. of truly saccharine matter, and next, by subtraction, that of farinaceous matter present in it.
