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
Catalogue details

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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    viewed iis cai-lionic acid, i[.XX).j; hence the, ,i>as is frecjiieiitly called carbonic anhydride. Formerly the term acid was ai)plie(l, hy souk* chemists, indiiierently to the anhydrides a?id their comiiounds with wat(‘r ; carbon dioxide then received the name of “cai-honic acid fi,as,” by which it is still i>opularly known. iModern detinitions of an acid prechnh^ this name bciipa; now correctly applied to what are propei'ly termed anhydrides. 60. Carbonates. With the exception of those of the alkalies, all carbonates are insoluble in water; many are, however, dissolved hy water containing; carbon dioxide in soluticm. The most int(>r(‘stin^’ example of this is the solution of considerable ([uantities of carbonate of lime in natural waters obtained from the chalk and other limestone <leposits. Such waters, altlK)U,iL;h perfectly clear, become turbid on hein<>- boiled fi’om tifteen to thirty minutes ; the hoilinc; drives off the carbon dioxide, and the calcium carbonate is precipitated in the insoluble state. The formation of carbonates is exemplitied by the passai^e of carbon ^dioxide yas into lime wat(‘r, i.e, a solution of lime in water, Call.jO.j; the insoluble calcium caihonate, or carbonate of lime, is ])roduced, and turns the clear solution milky. This foi’ins a useful and convenient test for the presence of carbon dioxide in any mixture of yases. ^lost carbonates are easily decoinjiosed hy the addition of an acid, with the formation of the coi-respondinc; salt of the acid used. Several instances of this action have been given w'hen describing methods for the jjroduc- tion of carbon dioxide. The acid- or hi-carbonates have one half only of the hydrogen! replaced by a metal; they may he produced by passing cai'bon dioxide gas tej excess through a solution of the normal carbonates of the nlkalies. The hicai-honates are readily decomposed hy heat into normal carbonates, free carbon dioxide, and waiter. 61. Compounds of Carbon with Hydrogen.—These are exceedingly numei'ous ; an account of some of those of most importance will he given when desciibing the organic bodies more particularly associated with our subject. As a gi'ou}!, they are termed “hydrides of carbfjn.” 62- Nitrogen, No.—This gas constitutes about four-fifths, by volume, of th(‘atmosf)hei'(‘; it is also a constituent of niti ic acid and its salts, and of many animal and vegetable substances. Nitrogen is colourless, odourless, tasteless, non inllammahle, and a non-su])portei'of combustion. It does not leailily enter into combijiation with othei- (dements, and in the free state is marked ratluu- by its neutral (pialities than by any [lositive characteristics. In th(( uncombined state its prineijial function is that of a diluting agent in the atmosphen*. Although not an active element, niti'ogen h^rms an extensive scudes of compounds. 63. The Atmosphere. -It has already been stated that th(> atmosphere c(jnsists essentially of oxygen and nitrogen ; thes(> gasc's are not unit(‘d in any way, hut sim])ly form a nuadianical mixtin-e. In addition to tlu; nitrogen and oxygen, air contains small (plantities of carbon dioxide;, water vapour, and traces of othiu' substances. Suh- joimid is a table showing its average composition :—
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