american hand book of the daguerreotype-第13部分

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trong　sulphuric　acid。　It　readily　dissolves　the　silica　in　glass；　and　consequently　cannot　be　kept　in　a　vessel　of　that　material。　　It　is　prepared　and　kept　in　lead。　It　is　employed　in　accelerators　on　account　of　its　fluorine。

One　small　drop　on　the　tongue　of　a　dog　causes　death。　The　operator　who　wishes　to　use　it　should　pour　some　of　the　liquid　for　which　he　intends　it　into　a　graduate；　or　other　vessel；　and　then　add　the　desired　quantity　of　acid。　If　by　accident　any　of　the　spray　should　fall　upon　the　skin；　it　should　at　once　be　copiously　drenched　with　water。

Sulphuric　Acid。There　are　two　sorts　of　this　acid：　one　is　an　oily；　fuming　liquid；　this　is　made　in　Nordhausen；　in　Saxony；　and　is　commonly　called　〃Nordhausen　sulphuric　acid；〃　or　oil　of　vitriol。　　The　other　which　is　the　kind　used　in　connection　with　the　Daguerreotype；　is　common　sulphuric　acid。　It　is　somewhat　thinner；　and　when　undiluted　is　not　fuming。　This　acid　may　be　obtained　in　a　solid　and　dry　state；　called　anhydrous　sulphuric　acid。

The　common　sulphuric　acid　is　made　by　burning　sulphur；　which　forms　sulphurous　acid。　　To　convert　this　into　sulphuric　acid　and　gain　more　oxygen；　nitric　acid；　which　is　rich　in　that　body；　is　added。　It　forms　a　limpid；　colorless　fluid；　of　a　specific　gravity　of　1。8。　It　boils　at　620　deg。；　it　freezes　at　15　deg。　It　is　acrid　and　caustic；　and　intensely　acid　in　all　its　characters；　even　when　largely　diluted。

Its　attraction　for　basis　is　such　that　it　separates　or　expels　all　other　acids；　more　or　less　perfectly；　from　their　combinations。　Its　affinity　for　water　is　such　that　it　rapidly　absorbs　it　from　the　atmosphere；　and　when　mixed　with　water　much　heat　is　evolved。　It　acts　energetically　upon　animal　and　vegetable　substances；　and　is　a　poisonous；　dangerous　substance　to　get　on　the　skin。　It　is　a　powerful　oxidizing　agent；　hence　its　use　in　the　galvanic　battery；　for　which　purpose　it　is　mostly　used　by　the　Daguerreotypist。　The　fumes　of　this　being　so　much　more　offensive　than　nitric　acid；　the　latter　is　sometimes　used。　　It　is　also　employed　in　some　of　the　more　sensitive　accelerators。


ACCELERATING　SUBSTANCES。

Remarks　on　the　Accelerating　substances　Used　in　the　Daguerreotype。　I　have　now　arrived　at　a　point　in　this　work；　where　the　eye　of　the　Daguerreotype　public　will　intently　search　for　something　new。　This　search　will　prove　in　vain；　at　least　so　far　as　regards　those　who　have　enjoyed　and　embraced　the　opportunities　for　studying　the　principles　of　our　art。　　Every　experienced　operator　has　in　a　degree　become　familiar　with　the　mechanical　uses　of　all　the　agents　employed；　while　I　fear　but　few　understand　the　properties；　and　laws　governing　those　properties；　which　are　so　indispensable　to　produce　an　image　impressed　upon　the　silver　surface。

There　are　three　substances　which　form　the　bases　for　producing　a　Daguerreotype；　silver；　iodine　and　bromine。　Each　forms　a　separate　body　which　is　indispensable　to　the　operators　success　as　the　art　is　now　practiced　in　America。　With　these　three；　compounds　of　great　variety　are　formed。

The　silver　surface　is　first　thoroughly　cleaned　and　freed　from　all　organic　matter；　then　exposed　to　vapor　of　iodine；　producing　an　iodide　of　silver。　The　plate　upon　which　is　this　salt；　is　again　exposed　to　the　vapor　of　bromine；　forming　a　bromo…iodide　of　silver；　a　salt　also。

As　most　of　the　various　accelerators　are　compounds　of　bromine；　with　either　chlorine　or　fluorine　combination；　they　partake　somewhat　of　the　nature　of　these　latter；　giving　results　which　can　be　detected　by　the　experienced　operator。　Thus　muriatic　acid　is　added　for　its　chlorine；　which　can　generally　be　detected　by　the　impression　produced；　being　of　a　light；　soft；　mellow　tone；　and　in　most　cases　presenting　a　brilliant　black　to　that　colored　drapery。　Those　who　wish　to　experiment　with　agents　for　accelerating　substances；　should　first　study　to　well　understand　their　peculiar　nature　and　properties；　as　well；　also；　to　endeavor　to　find　out　what　will　be　the　probable　changes　they　undergo　in　combination　as　an　accelerator。　　This　should　be　done　before　making　the　experiments。　　From　the　foregoing　it　will　be　seen　that　numerous　compounds　are　formed　from　the　same　basis；　and；　consequently；　it　would　be　a　waste　of　time　and　a　useless　appropriation　to　devote　more　of　our　space　than　is　necessary　to　give　the　principal　and　most　reliable　combination。

In　America；　the　words　〃Quick〃　and　〃Quick　Stuff；〃　are　more　generally　used　for　and　instead　of　the　more　proper　names；　〃Sensitives；〃　or　〃Accelerators；〃　etc。　As　it　has　by　use　become　common；　I　frequently　use　it　in　this　work。

Liquid　Accelerator；　No。　1。This　mixture　was　used　by　me　in　1849；　and　is　given　as　it　appeared　in　my　〃System　of　Photography；〃　published　at　the　above　date：

Take　pure　rain　or　distilled　water；　one　quart；　filter　through　paper　into　a　ground　stopper　bottle；　and　add；　for　warm　weather；　one　and　a　half　ounce　chloride　of　iodine；　or　for　cold；　one　ounce；　then　add　one　ounce　bromine；　and　shake　well。　Now　with　care　not　to　allow　the　vapor　to　escape；　add　drop　by　drop；　thirty　drops　of　aqua　ammonia；　shaking　well　at　each　drop。　　Care　must　be　taken　not　to　add　more　at　a　time；　as　it　evokes　too　much　heat。　This　mixed；　in　equal　proportions　with　John　Roach's　quick；　forms　an　excellent　chemical　combination。　　For　this　purpose；　take　one　and　a　half　ounce　of　each；　to　which　add　ten　ounces　water；　for　warm　weather；　or　from　six　to　seven　for　cold。　　Pour　the　whole　into　a　large　box；　and　it　will　work　from　two　to　four　months。　I　am　now　using　（l849）　one　charged　as　above　which　has　been　in　constant　use　for　three　months；　and　works　uniformly　well。　The　above　is　right　for　half　or　full　size　boxes；　but　half　of　it　would　be　sufficient　for　a　quarter　size　box。

Coat　to　the　first　shade　of　rose　over　iodine；　change　to　a　deep　rosy　red　over　quick；　and　black　about　one　tenth　the　first。

I　would　not　now　recommend　the　addition　of　〃John　Roach　s　quick；〃　as　I　believe　equally　good　results　can　be　produced　without　it。　This　liquid　is　now　used　by　many；　and　is　very　good　for　taking　views。

Lime　Water　Quick。This　mixture　is　more　used　at　present　than　all　the　other　liquids　ever　introduced。　　It　produced　the　most　uniform　results；　giving　the　fine　soft　tone　so　characteristic　in　pictures　produces　from　accelerators　containing　chlorine。　To　one　quart　of　lime　water　（this　can　be　had　of　any　druggist）　add　one　and　a　half　ounce　of　pulverized　alum。　This　should　be　shook　at　intervals　for　twentyfour　hours；　then　add　one　ounce　of　chloride　of　iodine　and　three　fourths　ounce　of　bromine。

Lime　Water。This　is　easily　prepared　by　putting　lime　into　water；　say　a　piece　of　quick…lime　about　the　size　of　an　egg　into　one　quart　of　water。　This　should　be　shook　occasionally　for　two　or　three　days　and　allowed　to　settle；　when　the　water　can　be　poured　off　and　used。

Use。To　one　part　of　quick　add　six　parts　of　water；　coat　to　a　light　yellow　over　the　iodine；　to　a　rose　color　over　the　quick；　and　recoat　about　one　tenth。　The　above　coating　may　be　increased　or　diminished；　it　matters　not；　so　that　there　is　not　too　much；　and　the　proper　proportions　are　preserved。　Some　add　to　the　above　a　small　quantity　of　magnesia；　say　about　a　teaspoonful　to　the　quart　of　liquid。

Liquid　Accelerator；　No。　2。The　following　was　for　a　long　time　used　by　one　of　the　first　houses　in　the　United　States；　and　probably　was　one　of　the　first　liquids　ever　used。　It　produces　a　fine…toned　picture；　but　is　not　considered　as　sure　as　the　lime　water　quick：

Take　rain　water　one　quart；　add　pulverized　alum　until　it　is　a　little　sour　to　the　taste；　and　a　small　piece；　say　one　half　inch　square；　of　magnesia。　Filter　through　paper；　and　add　chloride　of　iodine　one　half　ounce；　bromine　sufficient　to　take　it　up；　which　is　a　little　less　than　half　an　ounce。

Charge　with　one　of　quick　to　six　of　water；　coat　over　iodine　to　a　soft　yellow；　nearly；　but　not　quite；　bordering　on　a　rose；　over　quick　to　a　dark　purple；　or　steel；　and　back　one　sixth　to　one　tenth。

Wolcott's　American　Mixture。Van　Loan　Quick。This　mixture　was　first　formed　and　used　by　T。　Wolcott　&　Johnson　and　gained　great　celebrity　for　its　productions。　　I　have　now　a　bottle　hermetically　sealed　that　contains　about　a　half　ounce　of　this　mixture　prepared　in　1841　by　John　Johnson；　now　a　resident　of　this　city；　and　the　former　partner　of　Mr。　Wolcott。　The　preparation　of　this　mixture；　as　furnished　by　Mr。　Johnson　himself；　is　given　as　follows：

〃One　part　of　bromine；　eight　parts　of　nitric　acid；　sixteen　parts　of　muriatic　acid；　water　one　hundred　parts。　This　mixture　should　be　allowed　to　stand　for　several　days；　it　improves　by　age。

〃Use。A　few　drops　say；　6　to　12；　of　this　mixture；　should　be　put　into　about　6　or　8　ounces　of　water；　it　will　require　frequent　replenishing　by　the　addition　of　a　few　more　drops。　　The　plate　should　be　coated　over　the　dry　iodine　to　a　red　just　bordering　on　a　slate。　and　then　exposed　to　the　mixture　only　sufficiently　long　to　change　the　color。　If　this　is　not　done　in　less　than　six　seconds　it　is　not　strong　enough。　Re…coat　over　the　iodine　full　one　fourth　as　long　as　first　coating。〃

This　exceedingly　volatile　compound　is　difficult　to　control　from　its　instability；　it　is　but　little　used。　　The　impressions　successfully　produced　by　this　mixture　are　very　brilliant；　and　possess　a　pleasing　peculiarity。


DRY　SENSITIVES。

Hydrate　of　Lime。The　operation　by　which　water　is　combined　with　lime　is　called　slaking。　　Take　a　piece　of　quick　lime；　common　lime　used　in　mortar；　and　immerse　it　in　warm　water　for　about　fifteen　seconds；　then　place　it　in　an　iron　or　tin　vessel。　It　will　soon　begin　to　swell；　evolving　a　great　deal　of　heat　and　emitting　steam；　and　soon　falls　into　a　fine　powder；　hydrate　of　lime。　This　should　be　well　stirred　and　allowed　to　cool；　and　then　bottled　in　order　to　prevent　it　from　giving　off　the　hydrate　and　recovering　the　carbonic　acid　from　the　atmosphere。　The　last　is　detrimental　to　its　use　with　bromine；　and　is　one　cause　of　the　complaint　that　〃it　will　not　take　bromine。〃　The　hydrate　of　lime　should；　not　be　dried　over　a　heat；　as　has　been　supposed　by　many；　for　in　that　case　the　hydrogen　is　expelled　and　it　returns　to　a　carbonate。　It　is　advisable　to　cool　it　in　a　damp　place　like　a　ground　cellar。　Much　of　the　lime　in　our　market　will　not；　except　it　be　quite　damp；　combine　with　the　bromine。　　This　is　owing　to　impurities。　Nothing　is　equal　to　oyster…shell　lime；　which　I　use　altogether。

Bromide　of　Lime。In　preparing　large　quantities　of　this；　we　adopt　the　following　method：　　F