A text-book of the science and art of bread-making : including the chemistry and analytic and practical testing of wheat, flour, and other materials employed in baking / by William Jago.
- William Jago
- Date:
- 1895
Licence: Public Domain Mark
Credit: A text-book of the science and art of bread-making : including the chemistry and analytic and practical testing of wheat, flour, and other materials employed in baking / by William Jago. Source: Wellcome Collection.
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![INTIiODUCU'OUV. <l(‘nn‘t“ of this sonsatioii, a Ixxly is said to 1)(> cold, warm, or liot. TIk; (.•onditions wliioli produce tliis sensation of warmtii also cause otliei’ wi'll niark(‘d cliany<‘s in tlie jiliysical condition of substances. Tlie ifcneral eil'ccts of heat are to cause Ijodies as tliey yet liot to e.xpand in voluna*; furlliei', solids art'reduced to tlu' li(|uid state, and, with still further increments of heat, liquids arc' converted into yases. d'hec opposite' seric's of chanyes occur as heat is abstracted ficim bodic's. I'roin the c'xplanation of I'^orce yivc'ii in the juecediny parayrapli, it will be undc'rstood that thc'sc changes ai'c not accompanied bv any addition or diminution of weight. On the contrary. Heat is viewed as a form of Force, and is regarded as a mode or variety of internal motion of the particles of bodies - the hotter they are, the more violent and energetic is this motion. 5. Measurement of Heat: Temperature. -The earliest and most accessilile measure to be applied to beat is that of the sc'nsation of warmth before relVrred to, and according to whether a body to the touch is hot or cold, it is said to be of high or low tc'iiiperature. Temjiei-ature is, in fact, the measure of what is popularly termed “how hot a body is it will be seen on consideration that this depends on the power the body has of imparting heat to anothei’ body. Tlius, if when the hand is thrust into water, the water is able to yield heat to the hand, it is said to be “hot,” while if it robs the hand of heat it is .said to be “ cold.” The measure of this jiower is termed temperature, and is more exactly embodied in the following detinition :—The temperature of a bociy is a measure of the intensity of its heat, and is further defined as the thermal state of a body considered with reference to its power of communicating heat to other bodies. 6. The Thermometer —Foi- scicntilic, and also foi- most to'clinical purposes, tlu' sc'iisations are Jiot suthcic'ntly accurate mc'thods of ineasuiing temperature'; accoi(liiigly tempc'rature is usually mc'asured by certain of the cth'cts which lu^at produces: tlu' most convenient for this purpose', is the expiinsion eef liepiiels with an e'h'veitiem of temperiitui'e. Feir the' generiil jeurpnses ejf tem])Ci;iture' me'asin-e'ine'nt, the metal mercui-y is the meest cemve'ihent sidistance. This hepiiel, enclerse'el in a suitable ve'ssel, ceenstitute's the' temieerature-me'asui'ing instrume'iit te'rnu'el a thei’ineeine'te'r. In cenistructing ;i the-i'iimmcter, a bulb is bhewn at one e'liel eif a ghiss tube; eef very narreew beere' ; the bulb anel tube' are' ne'.xt lilh'el with tai'efully jairith'd me'i’cury ; this is beiih'el, anel thus all air anel meeisture are' didven eeut e>f the tube; tiie eejie'ii e'liel is then he'i-meticallv s('ale*el by fusing the glass itse'lf. At this stiige' the' bulb anel a [xertion of the' tedie' are' tille'el with me'rcury, the; re'inaineh'r eef the* tube being a vacuum, save' for the' pre'se'iu-e' of a nnnute' epiantity eef mercury \'a])e)ur. ()n he'ating the; bulb eef this instrument, the nu're.'ury e'.X])anels anel idse's cemsieh'i'Jibly in the' ste'in. d hi'eiughout any beeely, eu- se'iic's eif beeelies in contact with e'ach eetlici', he'iit has :i te'iieh'ne'y te; see • listribute' it.se'lf that the whole' se'i'ie's shall be' at the' same' te'uijie'rature' ; cemse'epie'ntly if the; the'i’iimme'te'r be pl;i.e-e'el in contae't with the' beeely wheese' te-mpe'riiture; it is eh'sire'el to mcasuie', a re'elistributieui eef he'at](https://iiif.wellcomecollection.org/image/b29315104_0035.jp2/full/800%2C/0/default.jpg)
