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preface to fifteenth edition

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11.118 SECTION 11<br />

Potassium carbonate, KCO93N: 2 3 207 g per liter.<br />

Potassium chloride, KCl90.5N: 37gper liter.<br />

Potassium chromate, KCrO90.5N: 2 4 49gper liter.<br />

Potassium cyanide, KCN90.5N: 33gper liter.<br />

Potassium dichromate, KCrO90.5N (K 2 Cr 2 O 7 /8): 38 g per liter.<br />

2 2 7<br />

Potassium ferricyanide, KFe(CN)90.5N: 3 6 55gper liter.<br />

Potassium ferrocyanide, K 4 Fe(CN) 6 ·3H 2 O90.5N: 53 g per liter.<br />

Potassium hydroxide, KOH95N: 312 g per liter.<br />

Potassium iodate, KIO 90.5N (KIO 3 /12): 18 g per liter.<br />

3<br />

Potassium iodide, KI90.5N: 83gper liter.<br />

Potassium nitrate, KNO390.5N: 50gper liter.<br />

Potassium nitrate, KNO296N: 510 g per liter.<br />

Potassium permanganate, KMnO 90.5N (KMnO 4 /10): 16 g per liter.<br />

4<br />

Potassium pyrogallate (oxygen in gas analysis): weigh out 5gof pyrogallol (pyrogallic acid),<br />

and pour upon it 100 mL of a KOH solution. If the gas contains less than 28% of oxygen, the<br />

KOH solution should be 500 g KOH in a liter of water; if there is more than 28% of oxygen in<br />

the gas, the KOH solution should be 120 g of KOH in 100 mL of water.<br />

Potassium sulfate, KSO90.5N: 2 4 44gper liter.<br />

Potassium thiocyanate, KCNS90.5N: 49gper liter.<br />

Precipitating reagent (for group II, anions): dissolve 61 g of BaCl 2· 2H2O and 52 g of<br />

CaCl 2· 6H2O in water and dilute <strong>to</strong> 1 liter. If the solution becomes turbid, filter and use filtrate.<br />

Quinaldine red (indica<strong>to</strong>r): dissolve 0.1 g in 100 mL alcohol; pH range colorless 1.4–3.2 red.<br />

Quinoline blue, cyanin (indica<strong>to</strong>r): dissolve 1 g in 100 mL alcohol; pH range colorless 6.6–8.6<br />

blue.<br />

Rosolic acid, aurin, corallin, corallinphthalein, 4,4-dihydroxy-fuchsone, 4,4-dihydroxy-3-<br />

methyl-fuchsone (indica<strong>to</strong>r): dissolve 0.5 g in 50 mL alcohol and dilute with water <strong>to</strong> 100 mL.<br />

Salicyl yellow (indica<strong>to</strong>r): see alizarin yellow GG.<br />

Scheibler’s reagent (precipitates alkaloids, albumoses and pep<strong>to</strong>nes): dissolve sodium tungstate<br />

in boiling water containing half its weight of phosphoric acid (sp. gr. 1.13); on evaporation of<br />

this solution, crystals of phosphotungstic acid are obtained. A 10% solution of phosphotungstic<br />

acid in water constitutes the reagent.<br />

Schweitzer’s reagent (dissolves cot<strong>to</strong>n, linen, and silk, but not wool); add NH 4 Cl and NaOH <strong>to</strong><br />

a solution of copper sulfate. The blue precipitate is filtered off, washed, pressed, and dissolved<br />

in ammonia (sp. gr. 0.92).<br />

Silver nitrate, AgNO390.25N: 43gper liter.<br />

Silver sulfate, Ag2SO49N/13<br />

(saturated solution): stir mechanically 10 g of the salt in a liter<br />

of water for 3 hours; decant and use the clear liquid.<br />

Soap solution (for hardness in water): (a) Clark’s or A.P.H.A. Stand. Methods—prepare s<strong>to</strong>ck<br />

solution of 100 g of pure powdered castile soap in a liter of 80% ethyl alcohol; allow <strong>to</strong> stand<br />

over night and decant. Titrate against CaCl 2 solution (0.5 g CaCO 3 dissolved in a concentrated<br />

HCl, neutralized with NH 4 OH <strong>to</strong> slight alkalinity using litmus as the indica<strong>to</strong>r, make up <strong>to</strong><br />

500 mL; 1 mL of this solution is equivalent <strong>to</strong> 1 mg CaCO 3 ) and dilute with 80% alcohol until<br />

1mLof the resulting solution is equivalent <strong>to</strong> 1mLof<br />

the standard CaCl 2 making due allowance

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