An introduction to practical chemistry : including analysis . bO,P05) oncharcoal, and observe the semi-transparent crystallineappearance of the bead on cooling (412).1 116. Heat a little oxide of zinc (ZnO)on charcoal; observe that it assumes ayellow color when heated, but becomeswhite again on cooling. 117. Notice the change of color thatensues when chromate of lead (PbO,Cr03)is gently heated, and observe whether theyellow color returns on cooling. 118. Repeat the experiment with redoxide of mercury (Hg02), taking care thatthe heat is not raised so high as to causedecomposition (109). 119. Mi
An introduction to practical chemistry : including analysis . bO,P05) oncharcoal, and observe the semi-transparent crystallineappearance of the bead on cooling (412).1 116. Heat a little oxide of zinc (ZnO)on charcoal; observe that it assumes ayellow color when heated, but becomeswhite again on cooling. 117. Notice the change of color thatensues when chromate of lead (PbO,Cr03)is gently heated, and observe whether theyellow color returns on cooling. 118. Repeat the experiment with redoxide of mercury (Hg02), taking care thatthe heat is not raised so high as to causedecomposition (109). 119. Mix together a little chalk (CaO,C02) and char-coal, and ignite the mixture in a tube; carbonic oxide When charcoal is used as a support in blowpipe experiments, itshould be cut into slices about the third of an inch in thickness, havinga small cavity scooped out with the point of a knife, in which to lodelthe substance to be heated. The charcoal maybe conveniently heldduring the experiment in a loop of tin plate, in the manner shown inr i<£. 4y. Fig. Charcoal-holder. THE MOUTH BLOWPIPE. 61 gas is given off; which, if formed in sufficient quantity,will burn with a blue flame. CaO,C02+C=CaO+2CO. 120. Heat a small crystal of carbonate or any othersalt of soda on platinum ware (which should be fusedinto a glass handle, and bent at the end, as shown inFig. 48), and observe the intense yellow color it com-municates to the blow7pipe flame. Then wash the wire,and compare its action on the flame with that causedby the soda. 121. Repeat the experiment, using nitrate of strontia(SrO,N05) instead of the soda: the color of the flamewill become crimson. 122. Heat a little chalk or marble (CaO,C02) on char-coal, and note the dazzling white light which is pro-duced, showing that the illuminating power of flame isnot dependent only on the degree of heat, but on thepresence of some solid matter in the flame ; since theblowpipe flame, which heats it, and which is of courseat least as hot
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectchemistry, bookyear18
