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

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.

79/740 page 47

$])oiDt M'liore tlio ^■apour l)e_^ins to coiulonsp, tlial when alooliol is jUH'sout, tlie distillate; trickles down the siilt's of the tube in pi;culiar oily looking drops or “tears.” This ap])(;arance ceases as soon as the* whole* of the idcohol has distilleel otV. Very minute* ejuantities of alcohol sullice te) proeluce this eti'ect. Another anel more delicate* method for its detec¬ tion depends on the preeeluction of ioeloform. This beeely has the synd)ol 4TII5, anel is .similar in constitution to chleeroform, CJICI.,. The* lie]uiel uneler examination should tiist be elistilleel, iind the; te*sts ;ip])li(*el tee the* tirst })e)rtie)n of the elistillate. Ten c.c. are to lee take*n and rendere*d alkedine by the aelelitieen of about a eiuarter of a c.c. (live or si.x elreeps) of a 10 per cent. se)lution of sodium hyelriite ; the liejuid must next be; warme*d to abeeut bO C., anel then a solutieen eef potassium ioelide*, satu- rateel with ieeeline, aelded elreep by elroj) until a slight excess of free ioeline is present; this is indicated by the liejuid acejuiring a ])e*rmanent sherry yellow tint. The liejuid must next be just decolourised by the addition of a minute ejuantity eef the seKlium h3ulrate solution. If there be an\’ alcolieel jiresent, ei yellow crj’stalline pi-ecijeitate of ieedeeform gradualh* forms. Certain other organic comj)Ounels, however, are capable of jeroducing the same reaction. 92. Methylated Spirits of Wine .—Alcoholic liejuoi's are sub¬ ject to a high duty; ceenseejuently, for jmrjeoses other than the jjroduction of drinkable s})irits, the Excise authorities permit the sale, duty free, of a mi.xture of nine volumes of rectitied sjjirit with one voluim* of com¬ mercial w(jod sj)irit. This mi.xture is known as “ metlydated sjiii'its of wine ; ” the imj.)urities of the wood spirit impart a flavour which renders the whole absolute^' undrinkable, excejit to the j)alates of the most <lebased di})Somaniacs. For most laboratory oj)erations, m(*thylated sjiirits can be used as a substitute for rectiti(;d sj)irits of wine : for <ielicate })urj)Oses it is well to re-distil the sjiirits jirior to use. Methy¬ lated sjiirits ma}'be rendered almost ab.solute liy adding aliout one-third of its weight of recenth' burned (juicklimo, and thoroughly shaking: the mixture must be allow(*d to stand some three or four daj’s, and the shaking rejieated two or three times daihx The sjiirit must then bt* distilled, jirecautions being taken to jirevent tin; temji(*ratur(* unduly rising. The still should be lix(*d in a watt*r bath, consisting nf an iron saucejian containing brine. The clear jiortions of the sjiirits should tirst be jioured into the still, without disturbing the .sedim(*nt, and distilled to dryness ly* ajijilication of ht*at to the water bath. Can* must be taken that the bath do(*s mjt boil dry. The J)asty mass of lime may next be jilaced in the still, jireferalily in small (juantit,i(*s at a time, and h(*at(*d by tin; bath so hmg as any alcohol distils over. An (*tlicient condensing worm must be used, ami tin; tube connecting it w’ith the still ought to be a long one. At the close of the oj)(*ration the lime may lx* removed from the ves.sel used as a still ly^ soaking with watei*. 93. Propyl, Butyl, and Amyl Alcohols. - The.s(; bodi(*s are jinxJuced in small (juantities during fermentation. d’h(*y all boil at a. higher tempei-atun; than ethyl alcohol, and aix; found in the* r(*sidual liijuor after most of the sjiirit has been distilled over. Projiyl alcohol occurs in the residues of the distillation of the ferment(*d liijuor of tin*$