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preface to fifteenth edition

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PRACTICAL LABORATORY INFORMATION 11.121<br />

Tropeolin OO, orange IV, sodium p-diphenylamino-azobenzene sulfonate, sodium 4-anilinoazobenzene-4-sulfonate<br />

(indica<strong>to</strong>r): dissolve 0.1 g in 100 mL water; pH range red 1.3–3.2<br />

yellow.<br />

Tropeolin OOO, sodium -naphtholazobenzene sulfonate (indica<strong>to</strong>r): dissolve 0.1 g in<br />

100 mL water; pH range yellow 7.6–8.9 red.<br />

Turmeric paper (gives a rose-brown coloration with boric acid): wash the ground root of turmeric<br />

with water and discard the washings. Digest with alcohol and filter, using the clear filtrate<br />

<strong>to</strong> impregnate white, unsized paper, which is then dried.<br />

Uffelmann’s reagent (gives a yellow coloration in the presence of lactic acid): add a ferric<br />

chloride solution <strong>to</strong> a 2% phenol solution until the solution becomes violet in color.<br />

Wagner’s solution (phosphate rock analysis): dissolve 25 g citric acid and 1 g salicylic acid in<br />

water, and make up <strong>to</strong> 1 liter. Twenty-five <strong>to</strong> fifty milliliters of this reagent prevents precipitation<br />

of iron and aluminum.<br />

Wijs solution (for iodine number): dissolve 13 g resublimed iodine in 1 liter of glacial acetic<br />

acid (99.5%), and pass in washed and dried (over or through H 2 SO 4 ) chlorine gas until the original<br />

thio titration of the solution is not quite doubled. There should be only a slight excess of iodine<br />

and no excess of chlorine. Preserve the solution in amber colored bottles sealed with paraffin.<br />

Do not use the solution after it has been prepared for more than 30 days.<br />

Xylene cyanole-methyl orange indica<strong>to</strong>r, Schoepfle modification (for partially color blind opera<strong>to</strong>rs):<br />

dissolve 0.75 g xylene cyanole FF (Eastman No. T 1579) and 1.50 g methyl orange in<br />

1 liter of water.<br />

p-Xylenol blue, 1,4-dimethyl-5-hydroxybenzene-sulfonphthalein (indica<strong>to</strong>r): dissolve 0.1 g in<br />

250 mL alcohol; pH range (acid) red 1.2–2.8 yellow, and (alkaline) yellow 8.0–9.6 blue.<br />

Zinc chloride, ZnCl290.5N: 34gper liter.<br />

Zinc nitrate, Zn(NO 3) 2· 6H2O90.5N: 74gper liter.<br />

Zinc sulfate, ZnSO 4· 7H2O90.5N: 72gper liter.<br />

TABLE 11.49<br />

TLV Concentration Limits for Gases and Vapors<br />

Exposure limits (threshold limit value or TLV) are those set by the Occupational Safety and Health Administration<br />

and represent conditions <strong>to</strong> which most workers can be exposed without adverse effects. The TLV value is<br />

expressed as a time weighted average airborne concentration over a normal 8-hour workday and 40-hour workweek.<br />

Maximum allowable<br />

exposure<br />

Substance ppm mg · m 3 Toxicity<br />

Acetaldehyde 25 45 carcinogen<br />

Acetic acid 10 25<br />

Acetic anhydride 5 21<br />

Ace<strong>to</strong>ne 750 1780<br />

Ace<strong>to</strong>nitrile 40 67<br />

Ace<strong>to</strong>phenone 10 49<br />

Acetylene<br />

slightly narcotic<br />

Acrolein 0.1 0.23

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