american hand book of the daguerreotype-第8部分

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Rub　the　buff　leather；　holding　the　face　down；　with　the　sharp　edge　of　a　pair　of　shears　or　a　piece　of　glass。　　This　brings　out　any　portion　of　the　skin　which　may　have　become　matted　from　any　moisture；　and　also　takes　out　any　substance　imbedded　in　it；　and　prevents　it　from　scratching。　　Then；　with　a　stiff　brush；　rub　the　buff　well；　and　it　will　be　found　to　work　well。　This　same　process　employ　on　wheels　and　hand　buffs　every　morning；　or　oftener；　as　occasion　requires。

Preparing　Buffs。Two　of　these　are　necessary。　　That　part　of　the　stick　to　be　covered　should　be　about　eighteen　or　twenty　inches　long；　and　three　wide；　and　made　crowning　on　the　face　from　one　end　to　the　other；　about　one　half　inch。　Before　covering；　these　are　to　be　padded　with　two　or　three　thicknesses　of　Canton　flannel。　　The　buff　should　not　be　too　hard；　but　padded　with　flannel；　so　that　by　drawing　it　over　the　plate；　it　may　touch　across　the　surface。　The　only　proper　material　for　buffs　is　prepared　buckskin；　and　if　prepared　in　a　proper　manner；　this　needs　nothing　but　to　be　tacked　upon　the　stick。　There　are　several　varieties　of　wheels　employed；　the　one　most　generally　adopted　is　Lewis'　patent；　which　consists　of　several　varieties　of　wheels。　Any　operator　can　make　a　suitable　wheel　on　the　same　plan　of　a　turning　lathe。

To　Clean　Buckskins。When　the　operator　is　compelled　to　purchase　an　unprepared　buckskin；　the　following　is　a　good　process　for　cleaning　it：　There　is　always　in　the　buckskin　leather　that　is　purchased；　more　or　less　of　an　oily　matter；　which　is　acquired　in　its　preparation；　sometimes　even　amounting；　to　a　third　of　its　weight。　The　following　is　the　mode　of　ridding　it　of　this　noxious　ingredient：　Dissolve；　in　about　six　or　seven　quarts　of　filtered　water；　about　five　ounces　of　potash；　when　dissolved；　wash　with　the　solution　an　ordinary　buckskin；　when　it　has　been　well　stirred　in　the　liquid；　the　water　becomes　very　soapy；　owing　to　the　combination　of　the　potash　with　the　oily　matters　contained　in　the　skin。　　Throw　away　this　solution　and　use　some　fresh　water　without　potash　and　rather　tepid；　change　it　several　times　until　it　remains　quite　limpid。　Then　gently　stretch　the　skin　to　dry　in　an　airy　shaded　place。　When　thoroughly　dried；　rub　it　well　between　the　hands。　It　thus　becomes　very　pliant　and　velvet…like。

Reflectors　for　Taking　Views。There　have　been　excellent　cameras　introduced　for　taking　views；　but　the　time　of　exposure；　which　is　increased　in　proportion　to　the　focal　length；　is　considered　an　objection；　consequently　many　adhere　to　the　old　plan　of　using　the　speculum；　or　rather；　substitute　a　mirror。　I　now　have　one　which　I　have　used　for　several　years　and　find　it　equal　to　any　article　of　the　kind　have　ever　tried。　One　is　easily　made　by　a　tin　man；　at　a　trifling　expense。　Procure　a　piece　of　best　plate　looking…glass；　two　and　a　half　by　five　inches　for　a　quarter；　or　four　by　eight　for　a　half…sized　camera；　put　a　piece　of　pasteboard　of　the　same　size　on　the　back；　to　protect　the　silvering；　and　stick　around　the　edge　in　the　same　manner　as　in　putting　up　a　picture。　　Take　a　sheet　of　tin　for　the　large　size；　or　a　half　sheet　for　the　other；　place　the　glass　crosswise　in　the　centre；　bend　the　ends　of　the　tin　over　the　edge　of　the　glass　and　turn　them　back　so　as　to　form　a　groove　to　hold　the　glass；　and　still　allow　it　to　slide　out　and　in。　These　ends　of　the　tin　must　be　turned　out　flaring；　that　they　may　not　reflect　in　the　glass。

Have　a　tin　band　about　an　inch　wide　made　to　fit　close　on　the　end　of　the　camera　tube；　place　it　on；　and　taking　the　tin　containing　the　glass；　bring　it　to　an　angle　of　forty…five　degrees　with　the　tube；　extending　nearly　the　whole　length　of　the　glass　in　front　of　the　lenses；　lap　the　loose　ends　of　the　tin　on　each　side　of　the　tin　rim；　and　having　your　camera　turned　on　the　side　to　throw　the　view　lengthwise；　arrange　the　exact　angle　by　examining　the　image　on　the　ground…glass。　When　you　have　it　exactly　right；　hold　it　while　it　is　soldered　fast　to　the　band。　Take　out　your　glass　and　stain　the　tin　black；　to　prevent　reflection。



CHEMICALS。

CHAPTER　III。

Bromine　and　its　CompoundsIodine　and　its　Compounds　Chlorine　and　its　compoundsCyanide　of　Potassium　Hyposulphite　of　SodaHyposulphite　of　GoldNitric　Acid　Nitro…Muriatic　AcidHydrochloric　AcidHydrofluoric　Acid　Sulphuric　AcidAccelerating　SubstancesLiquid　Sensitives　Dry　Sensitives；　etc。；　etc。

BROMINE。

An　article　so　extensively　used　in　the　practice　of　the　Daguerreotypic　art　as　Bromine；　is　deserving　of　especial　attention；　and　accordingly　every　person　should　endeavor　to　make　himself　familiar　with　its　properties　and　applications。

History。This　element　was　discovered　in　1826　by　M。　Balard；　in　the　mother…liquor；　or　residue　of　the　evaporation　of　sea…water。　It　is　named　from　its　offensive　odor　（bromos；　bad　odor）。　In　nature　it　is　found　in　sea…water　combined　with　alkaline　bases；　and　in　the　waters　of　many　saline　springs　and　inland　seas。　The　salt　springs　of　Ohio　abound　in　the　compounds　of　bromine；　and　it　is　found　in　the　waters　of　the　Dead　Sea。　　The　only　use　which　has　been　made　of　bromine　in　the　arts　is　in　the　practice　of　photography。　It　is　also　used　in　medicine　In　a　chemical　point　of　view　it　is　very　interesting；　from　its　similarity　in　properties；　and　the　parallelism　of　its　compounds　to　chlorine　and　iodine。

Dr。　D。　Alter；　of　Freeport；　Pa。；　is　the　only　American　manufacturer；　and　furnishes　all　of　the　〃American　Bromine。〃　　Yet　we　understand　much　purporting　to　be　of　German　manufacture　is　prepared　from　that　made　in　Freeport。　　This　is　done　by　individuals　in　this　city；　who　get　well　paid　for　the　deception。

For　the　successful　application　of　bromine　as　an　accelerating　agent；　we　are　indebted　to　Mr。　John　Goddard　of　London；　who　at　the　time　was　associated　with　Mr。　John　Johnson；　now　a　resident　of　this　city。

Preparation。The　mother…liquor　containing　bromides　is　treated　with　a　current　of　chlorine　gas；　which　decomposes　these　salts；　setting　the　bromine　free；　which　at　once　colors　the　liquid　to　a　reddish　brown　color。　　Ether　is　added　and　shaken　with　the　liquid；　until　all　the　bromine　is　taken　up　by　the　ether；　which　acquires　a　fine　red　color　and　separates　from　the　saline　liquid。

＇page　74＇

Solution　of　caustic　potash　is　then　added　to　the　ethereal　solution；　forming　bromide　of　potassium　and　bromate　of　potash。　　This　solution　is　evaporated　to　dryness；　and　the　salts　being　collected　are　heated　in　a　glass　retort　with　sulphuric　acid　and　a　little　oxide　of　manganese。　The　bromine　is　distilled；　and　is　condensed　in　a　cooled　receiver；　into　a　red　liquid。

Properties。Bromine　somewhat　resembles　chlorine　in　its　odor；　but　is　more　offensive。　　At　common　temperatures　it　is　a　very　volatile　liquid；　of　a　deep　red　color；　and　with　a　specific　gravity　of　3；　being　one　of　the　heaviest　fluids　known。　　Sulphuric　acid　floats　on　its　surface；　and　is　used　to　prevent　its　escape。　At　zero　it　freezes　into　a　brittle　solid。　　A　few　drops　in　a　large　flask　will　fill　the　whole　vessel　when　slightly　warmed；　with　blood　red　vapors；　which　have　a　density　of　nearly　6。00；　air　being　one。　It　is　a　non…conductor　of　electricity；　and　suffers　no　change　of　properties　from　heat；　or　any　other　of　the　imponderable　agents。　It　dissolves　slightly　in　water；　forming　a　bleaching　solution。

Chloride　of　Bromine。This　as　an　accelerating　agent　is　by　many　considered　superior

＇page　75＇

to　the　other　Bromide　combinations。　　It　can　be　readily　prepared　by　passing　a　current　of　chlorine　through　a　vessel　containing　bromine。　A　mixture　of　two　parts　muriatic　acid　and　one　of　black　oxide　of　manganese；　should　be　put　into　a　flask　having　a　bent　tube　to　conduct　the　chlorine　vapor　into　the　bromine　in　another　vessel。　This　last　vessel　should　also　be　supplied　with　a　bent　tube　for　conducting　the　combined　vapors　with　a　third　vessel　or　receiver。　On　the　application　of　the　heat　from　a　spirit　lamp　to　the　bottom　of　the　flask；　a　current　of　chlorine　gas　will　be　disengaged；　and　pass　into　the　bromine；　when　it　readily　combines；　and　gives　off　a　vapor；　which；　when　condensed　in　the　third　vessel；　forms　a　volatile　yellowish…red　liquid。　　It　is　best；　even　at　ordinary　temperature；　to　place　the　receiver　in　an　ice　bath。　For　manner　of　using；　see　farther　on；　under　head　of　Accelerators。

Bromides。A　bromide　treated　with　oil　of　vitriol；　disengages　chlorohyadic　acid；　but　vapors　of　bromine　are　constantly　disengaged；　at　the　same　time　imparting　a　brown　color　to　the　gas。　If　the　bromide　be　treated　with　a　mixture　of　sulphuric　acid；　and　peroxide　of　manganese；　bromide　is　only　disengaged。　A　solution　of　a　bromide　gives；　with　of　nitrate

＇page　76＇

silver；　a　light　yellowish　white　precipitate　of　bromide　of　silver；　which　is　insoluble　in　an　excess　of　acid；　and　readily　dissolves　in　ammonia。　The　precipitated　bromide　is　colored　by　light　like　the　chloride；　but　is　immediately　tinged　brown；　while　the　chloride　assumes　at　first　a　violet　hue。　The　bromides；　in　solution；　are　readily　decomposed　and　chloride　being　set　free；　colors　the　liquid　brown。

In　the　whole　range　of　heliographic　chemicals　there　is　probably　not　another　collection　less　understood　and　being　so　productive　of　interesting　investigation　as　the　bromides。

Bromide　of　Iodine。M。　de　Valicours　furnishes　us　with　the　best　method　for　preparing　this　mixture：

〃Into　a　bottle　of　the　capacity　of　about　two　ounces；　pour　thirty　or　forty　drops　of　bromine；　the　precise　quantity　not　being　of　importance。　　Then　add；　grain　by　grain；　as　much　iodine　as　the　bromine　will　dissolve　till　quite　saturated。　This　point　is　ascertained　when　some　grains　of　the　iodine　remain　undissolved。　They　may　remain　in　the　bottle；　as　they　will　not　interfere　with　the　success　of　the　preparation。

〃The　bromide　of　iodine　thus　prepared；　from　its　occupying　so　small　a　space；　can　very　easily　be　carried；　but　in　this　state　it　is　much　too　concentrated　to　be　used。　When　it　is　to　be　employed；　pour　a　small　quantity；　say　fifteen　drops；　by　means　of　a　dropping…tube；　into　a　bottle　containing　about　half　an　ounce　of　filtered　river　water。　It　will　easily　be　understood　that　the　bromide　of　iodine　can　be　used　with　a　greater　or　less　quantity　of　water　without　altering　the　proportion　which　exists　between　the　bromine　and　iodine。〃

This　article　forms　a　very　good　dry　accelerator；　and　is　by　some　persons　thought　superior　to　all　others；　as　it　works　with　great　uniformity；　and　is　less　liable　to　scum　the　plate　in　coating　at　high　temperatures；　or　when　the　thermometer　indicates