Essays on bleaching

82

Mamff'aclure of Nlarch in France.

we can thu~ establish the theory of what takes place in the preparation of atarch. These ~rains contain much starch~ the ligneous matter~ formin~ the husks (if the ~rain; a small variable quantity of gluten, albumen~ and certain saltd;, amongst others, the phosphate of li-me. The re-action of the ~lutex~ upon the starclb occasmns the formation of a little saccharine matter; the co,tinued ferment in the lnixtare, causes the .,]Ji~fflttmtsjlrmcntaliom and produces alcohol, and carbonic acid. Thi~ last is disengaged in the gaseous form~ and from thence are derived the rabbles 'a'likl arlsc~ and burst, atthe surface of the liq,ov. 'File .rid ['crmcJ~lalim~ i..mediately tbllows; the a o t t r IPttlt:'t" Itv( t'~'qt 'i V ~txt: l e s ' this fermentation, front which results a new quantit v . f ~i~.',,~;.'; and s.on aJ'(cr, the glvteu, by reason of the lar~_;c ( U;tl;tity ~.f a/.l)tc which it coniailis, an~i its facility of spont;me~.~s' altcrati(m. ~ives bhlh t. the pulrid/~rme~d.lion, which dcvehq)es amm..ia; tii ;~ ~le~ and tl e phosl~h'tte tf llme are, in l)art~ .liss~lved i. th,~ li~ uor by the, accti(" acid, and a.'e partly held in suspeI~ iol, l,: lht! l'eqHliOIL ()1~ these l~vin(:ij~lcs forms tl~e sour waters of which we have sp.keu. It oOen ha l, ),,~ (hat d,~ .s,~t~"re,lets, when they are poured upon the bruised 'zrain. in the tirol par( ()[' ill(! ~q~(w;tlion. subsid% without occasi(~tlh~g arl)' di>-vllga~vm¢,l~l, of ('acl~()ni(: acid gas, any sensible movet,ellt, of ally ol},'v (;ha,~e than Inaki~; all t]w. liquor thick~ gluey, andropv. This alteration, to which they havegive~ the name of the vlscous)'ermentutloa, although of little in~l)Ortancc here, is very remarkable: it is accidentally i)vcset~ted in miu~y other cases, and particularly in the treatment of sacchari~;e m.'ttters, where it is ahnost always in'uri(ms, and often occasions considerable loss. Uses.'--nJStarch is employed in many of the arts, although but in amall quantities: painters, coufectioi~evs, laumtresses} &c. make great u~e of it; physicians prescribe it as an aliment of a peculiar nature, aml a~ a medicine; but in this case, as also in the manufac~.ure ()f sugar fi'mn starch, they give the prel~rence to the starch, or fecula, of the Imtah). (~,mpo.~iti,m.~,~taH.h is formed in weight, according to M. Berzelius, of Carbon . . . . . . . . 43~481 ()xyg~!n . . . . . . . . . 49,455 llydrogen . . . . . . . . 7,064

100.

P.

ESSA'~ S ON B L E A C I H N G .

B21 James Rennie, ./1. ~IL L~ c{~fcr o~ Philosophy, ,S'c. 4"c., London. No.

I[[.--(~tlE.MI(?AL

AtII'N'I'S USI,iD IN BLEA(~II.IING.

SECTIO.U VlX. Continued. 4 . ~ 3 L ' . 7"cmzunt's Blcaching~ S.It, m" the Oxymuriute of' Lime. Ll.~ll,: ~a~ impregnated with chlorit~e, fiw the purposes of bleaching, at an early stag~; of the improvements we ave now detailing, by

M•. R~NNI~'S Essays on Bleaching.

8S

Watt, Henry, and Cooper; but it does not appear that it was by fl~em brought into their general practice, as they seem t o have prefei~d the simple water, or the oxvmurmte of potash, t was reserved for Mr, Charles T e n n a u t of Glasgow, to improve the process of making ~ it so as to render it both a cheap, convenient, and efficacious agen~ in hleachinz. ~: The first process which he adopted for tiffs purpose i has been already given. (Page 338, Vol. IL) He was deprived of the p,~tent he had for the manufacturing of this substance, in t e n s e , q ue~tce of a legal decision in the Court of Session. T h e loss of his patent stimulated Mr. T e n n a n t to new eflbrts of ingenious invention, :md lie succeeded in combining chlorine with lime, in the d r y way~ which renders it easily portable to any distance at a small exi~ense,t hi consequence of this, his business has increased to a prouigious amount~ while the bleaching processes have received grea~improve, ment. The ex.l)ense .als°' is. greatly lessened,. . as linie is. so mueh cheaper than the alkahes which used to be consumed for this purpose~ to a very great amount.~t '['he concrete oxymuriate of lime, or Tennant~s salt~ as it is called t/b file bleachers, is, wherl prepared for immediate use, diflhsed by agitation in a quantity of water. This is allowed to stand for some time, till any insoluble matter contained in the limt, is precipitated~ and the supernatant liquor remains transparent. The liquor thus clarified~ is drawn ott" anti diluted with a considerable proportion of water~ when .it is ready for the imlllersiorl of goods. This salt dif'/ers .so remarkably from nm-t o~]lers, tllal it calmer be procured from the ,~.l~liion. eitl~er in at dr~ m;tss, or i~ ~~'vslals, by evaporation; fi~r when ~ll, ll a s~hlli~m is t.~a/im-atlt.d, part of the acid escapes, and the rest i~ nu~:.tl) t onverted into limvhttic :,:i,I; s~ that, instead of oxymuriate ~,f liHle, m~lriate of liin~ is ~btained. T h e dlff salt can only be oblain~ll by 3h'. TcnnanC~ tn'oce~s of using dry lime, iu the ti,'st instance.

5.~7'ests for ascertaining the slrenglh of Ox~muriale of Lime. In treating of the other agents of bleachi~g, we have seen of how * The oxymuviates of harytes anct strontltes, which x~'erealso mentioned in his pat,.-nt, were found to be too expensive l%r practical purposes~ as the latter ~ubstauce couht not be procured in g'rcat quantity, and the fbrmer could with dii}iculty be separated t}'oln tile su]t:d~.uric acid with which it is usually found combined. ~ So ~reat is the redtlction of expense from this cause, that it was proved upovi oath, that, by usin~ oxvmuriato of lime, the consumption of ashes, in a sin.~lo bleaching.green, has b~cn reduced £3000 in vahle in one year. ~: In order to ])ro~lnce tills lmpm'tant agent, tile chlorine gas is sent into a re. ceivei5 similar to that tbrmerly described, which contains, in a pulverized forl~ the dry hydrate of limc¢ that is, lime slacked with the least possible quantity of water. 2'lie powdel', dm'ing the influx of the gas fi'om the distilling"apparatus, is continually ag'itated, an
~4

Ms. RzN~tz's

E,~'sa~ji~on Bteacltb~g.

much importance it is to the manufact,,rer~ to be able to ascertain the quantity (ff eflicient matter, in any of the substances of commerce, which he has occasion to nurchase. With respec~ to oxymuriate o| lime, this ou~hi[ perhaps,'to be still more atte,'~ded to, insomuch as it is the principal'agen{for producing pure whites. But [ am much mistaken, if any method has come into general use among bleachers, b y which the qualit': of a ~iven (tuantity of this substance can be as¢ertained.~Titev are under the" necessity, indee(, of ascertaining the bleachin~ ,)~wer of the diluted liquid, previous to immersing their got)ds, ~"vl:ich is commonly done by an indigo test, and in this way, by (~bservin~ the quantity of salt and the proportions of water used, they may make a rude guess, concerning the strength of the salt, when purchased; but this, at best. must be an inaccurate method of proceediu~. To reined ~' those inc~nveuiences, the ingenious Mr. l)alton instituted a course'of experiments, in which he was successful in obtaining a test of easy al;plicatinn ~ lbr ascertaining the purity of oxymuriate of lime. From these experiments it appears, that the green sulphate of iro,l is bv li~,- the best test of oxymu,'iate of lime. As the indigo test does re@ ~veil in ascetqaining tim strength uf the diluted liquor, and as it is yew generally used, I cannot well omit dctailinz the manner of its api;lication. Prepare a very dilute solution of i,~digo by dissolving, iu the usual way, a pound of the best Spanish in four pounds of concentrated sulphuric acid, which proportions will generally be sufficient to i~roduce saturation. When at[ the indigoes dissolved, one part, by measure, of this solution, is to be diluted with sixteen parts, ny measure, of water, when it will be fit for use. To obviate any deception which may arise from the dill'erence of strength in the indigo, it is best alwa)s to preserve some of a former preparation, ~u ('onq~are wit}, the new, when, by a little managemet~t, it may be made equal. 'the quantity el" water use~ is not [uaterial, prov~ided that; the same bleacher keep alu'ays to the same proportion. The strengtlt of the bleaching liquor, is deterrnined by the quantity of it, which is required tl~ destroy the colour of any g~ven portion of the test. lr~ practice, it is usual to have two graduated glass tubes, one fin" the test, the other for the liquor, by which arranzement the efflcien~: quanlities are seen by inspection.'Berthollet says he was infiu'med b y Mr. Watt, that the imligo test will not accurately show the strength of either ox~muriate of soda, m" of potash, and recommends a decoclion of cocl;ineal, as not being so liable to inaccuracy, or deceptiolx. From what I can learn, however, this has not been hmnd so convenient in practice, as the indigo test. Mr. Dalton's test from sulphate of iron, will soon, I imagine, supersede all others.

-NO. [V.~C}IEMI(;AL AND PIIYSICALNATUI[~OF STUFFS.

~o satisfactory account can ever be given of a chemical process,

unless all the substances which are emplo~ed in it be m i r m t e l y known, bo*h as In their general nature, and,'~f possible, as to t h e i r

MR. RE~Nm's Essays on Bleaching.

~t

composition when they are compounded: This has not beenpt0~ perly attended to in any of the works on bleaching which h~/ve f ~ ] ~ ~nto my hands, as none of them give any chemical account of t ~ substances which are to be operated upon. This deficiency I sl~ll attempt to supply, although I feel that my information is inadequate to do it justice, and in order to render it more perfect, it would reqtfire more laborious analytical and experimental research~ than either my ability or leisure will allow. I'have derived the best ~.art ,of the knowledge I have of this subject fi'om Home~ Fourcroy~ Kirwan, and Bancroft. Animal substances differ very much from vegetable, both in their physical structure arid chemical composition. Wool and silk, for example, are much looser in their texture, and have less adhesion between their constituent parts, than cotton and linen, and are therefore more disposed to combine with other matters which are brought into contact with them, and manifest stronger aftinities for tlm orillnarv a~ents of bleachitie:.? Their chemical composition is still more dtssi ~i at" fronl that of vegetables, I n conta|nln m a ,~reater proporhon of l,ydrozen, and varticularlv o f nitrogen, wh3ch]in vegetables, i s usuaIly l~esent in'but small "quantity. It is the tendency of these to assunte the gaseous fi~rm, which renders the adhesion o f the ultimate principles in silk~ and wool~ so slight.and easily overcome. When they are subjected to distillalion, these two prinei[Aes seem to unite, and form with oxygen the volatile alkali, which is sehlom deveh)ped in arty quantity from vexetabh's bv the r,'tm't, the several acids being theordina~:vpr
~

'"

~"

"

*

0 "=

fr

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* We would not, however, ire understood to infer from this, that a knowledg'e of the structure and composition of' the ultimate constituents of the substances ill question, will much assist I.tsill anticipating., without previous trial, the result of any process in bleaching; we merely infer that such knowledg'e may assist us toexplain upon what the effects produced depend, and may sug:ffest material improvements, both in efficiency and economy. Jf This is well illustrated by what takes place in dying' of a scarlet co]our~ tile woollen cloth which is sometimes edged with cotton, as the cotton, being" less easily affected, remains white :ffter the wool has acquired the required shade; the same will happen if cloth be made with cotton warp t~nd woollen w~,of, a~ has been experimentally shown by M. Dufay.--Banerofl.

86

M a . R]a~NIE's

Rssays on Bleaching.

nitrogen, separatin~ the fatty matter~ and forming carbonic and oxalic acMs. 'Itm suh)huric, extricates thmr hydrogen, a small pottnm ot their nitrogen, and leaves a carbonaceous residuum. The alkalies, again, destroy animal substances by combining with their oils, wb!cb sheath their causticity, and form soap, while they affect vegetabie~ but slightly. Silk is the least liable, of nil animal substances, to be acted upon by acids or alkalies, a~ it is more nearly allied than wool, to ~regetables, in i[s structure and composition. ~But I shall give a more spcdtk: descriptim~ of those differences, beginning with the animal substam:es. 1. SiK.--This substance is procured fi-om cocoons formed by the caterpillar of 1.he..]]01~lb]/:C ¢lWr{, el Linnmus, previous to its transfurmatim~ into a moth. It c~msists of tilaments of great tenuity and comparative strenuih, which am unil'm'mly covered by a very thin peIlicle of a Mother'us of gummy matter, which serves to render them stiR" aml el£~iic. Tht~v'are usually of a yellowish tinge, from the ¢ombimtii,m vf cohmrif~g matter, which M. gaum6 found to consist nf a re~ t p wfe :t y al imalizt;d, aflbrding~ by distiUation, the same pt'vd~u:ts a~ ~}tl~w animal matters, and the concre.te volatile alkali. (see aourn, tie Phys. 1795.) This it is necessary to remove, in order to render the l{!~re ptia~t, and manageable, for the manufacture of cloth, which is commol~ly done by means of soap, accordirlg to a proeess described by Berthollet. ~Besides this gummy and cokmrlng matter, M. [l.oard (Ann. de Chim.) found that there is a~mther sub~tance, like wax, whict~ requires t~ be remo~etl. He informs us that the g-urn is, commonly~. . i~l the proportion of .g4 t~er cent.,., tile colouring matter about 5a or 60, and tile wax seldom re,are than 1, and often only about half that proportion. The gummy substance is soluble in water, and w~uld be easily managed if the others were not present, for it tm'ortmmtelv happens that the colouring matter cannot be tiss ,lv :d by w ~le,'; ~t ~s, mwever, saluble in alcohol, and ~lso, together" with the animal wax, capable of being removed b}" all{aline leys or by s~mp.~: "l'he~silk procured ti'om tim cocoons nf~the Born• byx mm'~, sceuls (o tinier cons~ lerably m strength and composmon, according" • to tlt(:ditli'.'~tent place~." i lIn' ;, hich ' the insects',, live;i .but my information i~ too scanty to be abc to pont out those d flerences with ;precision. h~ India and China, si~k is procured from several other insects of the same trib% which is strikingly ditthrent from the common silk. Dr. Roxburgh (Lin. Trans.) tails us of a phalena. whose cocoons are remarkably saft. and white, or yellowish, but it being ditScult to wind off the silk,'it is spun like cotton, and • ~,

-¢

°

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.

It was found by 3Ir. M:ushatthat silk contains more carbon than any of the other substances employed in the mauui~acture of cloth, lte distilled, in the dry way, 200 grains of \vt~ke silk stut~, ~tnd during the process there was a violent discharge of bituminous flame and. smoke. The residmlm was formed into a caked coal of a dense compact structure; cellular, though not in the least brittle. The eolour wasiron-g~ay,with afalatshadeofeopper. When struck, it was sonorous in a high degree. It weighed 62 grs. and had consequeutly lost by the process 138 grs. Silk, then, is composed of 69 graina valatile matter, and ,~1 of oxide of earhon. (Phil, Nag. xxxiil, 4.)

Preparation of Tuscan Straw.

87

possesses a durability almost incredible, the life of one person being

seldom sufficient to wear out a garment of it. Its texture and c o ~ position must be very different tS.om common silk, as it will not bear washing in hot water. The Doctor mentions another sort of silk which is coarst, durable, and dark coloured, and much worn by the Bramins. The silk fi'om Nankin in China is naturally pure whlte~ but the Chinese, according to M. Baum6, (Journ. de Phys. 1798,) bleach a great quantity of common silk, and pass it for Nankin.

On the Growth and Preparation of the Straw usedfor Plait, in the "l~scan trade. "l'u~ Illghland Society of Scotland, in their list of Premiums for the present year, state, that " t h e y have ever)- reason to be satisfied with the success of tile premiums offered last year, and although the specimells produced in-consequence, have done uncommon credit both to the manufacturers, and to the operative people in this countr~j yet, the result of the inquiry wMch the society has been able to make into this important object, leads them to the conclusion, that "until farmers raise the straw fi;r sale, it is not likely that the manufacture of Leghorn bonnets will become general ill Scotland. If straw couhl be Rot to purchase at a rcasmmble rate ill Ibis emlllll')', the greatdifticullv in exte~dilJ~ the ,llal,llJ}/Ctll,'e wouhl Iw ren,oved." 'l'h~,~ have accotlliil=l) ,)lt'cred sevet'al premiums tbr this important ol)iect , slid the', add as lilllows:~ " 'l?hc fotlow!!~g obsevvati.ns have been extracted fi-om some valuable communicatmns which have reached the society fl'om Mr. Horace Hall of Florence, Mr. Boswell of Kingcausi% and others; and areinserted here• as, P erha Ps aftbrdin,,'~ information . . on some P oints of msnagement m the growth and preparatmn ot the straw used i n t h e Tuscan t,'ade, which may not yet be quite'familiar in this country." ~' The seed. from which the straw for plaiting' is grown, is a sn]all round gram of wheat, called g'rano marzuolo, or, more properly, .¢~'m~o 7imrzola,w. It is so calJed from being sown in t m month of March, and ditti~rs fi'om common wheat m appearance, from its rounder and shorter shape. It is an error to suppose hats are made fi'om ,'ye, (at any other grain in Tuscany. This marzolano straw is cultivated for tile sole purpose of being made into hats; and is grown chiefly in the vicinity of Flm'ence, and on the hills on both sides Of the valley of the Avn~). The growth of the straw is thus almost exclusively confined to a limiled part of the province of Tuscany. A l e r t years ago, the Pope aware of the source of wealth which this manufacture produced in that quarter, attempted to introduce the culture of it into his States. From the habits of the people, difference of soil or climate, or from all these causes conjoined, the plan did not succeed; and the Grand Duke of Tuscany having now allowed the prepared straw to be exported, the idea of cultivating itl elsewhere