The chemistry of plant and animal life . rvethe result. (2) Place a few drops of indigosolution in a test-tube containing 5 cc. ofwater, then add about 2 cc. of HNO3. Ob-serve the result. (3) Place a small pieceof copper in the test-tube containing theremainder of the acid. Observe the no reaction takes place, add a littlewater. Do not pour the contents of theflask into the sink or waste jars untilcool, otherwise the hot acid coming in contact with cold watermay cause spattering of the acid. Questions. (i) Why was H2SO4 used in the preparation of thiscompound? (2) What material suppl
The chemistry of plant and animal life . rvethe result. (2) Place a few drops of indigosolution in a test-tube containing 5 cc. ofwater, then add about 2 cc. of HNO3. Ob-serve the result. (3) Place a small pieceof copper in the test-tube containing theremainder of the acid. Observe the no reaction takes place, add a littlewater. Do not pour the contents of theflask into the sink or waste jars untilcool, otherwise the hot acid coming in contact with cold watermay cause spattering of the acid. Questions. (i) Why was H2SO4 used in the preparation of thiscompound? (2) What material supplied the NO3 radical? (3)Write the reaction which took place in the flask after heat was ap-plied. (4) Is HNO3 a solid, liquid, or gas? Why ? (5) What causedthe red fumes to be given ofE when the copper was added to thetest-tube? (6) Does HNO3 give off H when a metal is added to it?Why? (7) Why did the HNO3 bleach the indigo solution? (8)Why is ordinary HNO3 colored yellow? (9) Is HNO3 ^^ active orinert chemical ? (10) What is a nitrate?. Fig. 42.—Preparation ofnitric acid. 88 AGRICULTURAL CHEMISTRY 94. Properties.—When pure, nitric acid is a colorlessliquid; the commercial acid has a yellow color becauseof the presence of oxids of nitrogen. Nitric acid is anactive oxidizing reagent, and when metals, as copper andiron, are dissolved in it, brown fumes of NO2 are givenoff because the hydrogen, as soon as liberated, is oxidizedby the excess of acid and NO2 is formed. H + HNO3 =HjO + NOj. Nitric acid imparts a permanent yellowcolor to wool, silk, and all albuminous matter. 95. Importance.—In the laboratory, nitric acid is usedas an oxidizing agent. It is used commercially in thedyeing of cloth, although it has a tendency to weaken thewool fibers. Salts of nitric acid are important becausethey are of so much value as plant food, and particularlyin the manufacture of commercial fertilizer, where it sup-plies nitrogen. Potassium nitrate is used in the manu-facture of gunpowder.
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