I~KINOlINGTEMPERATURE OF SUBSTANCES nnett G. Melgaard, New Mexico State University, Cniversity Park . McCarty, Michigan State University, East Lansing
pf0,&~ 6 glasses, short length of softglass 3~ u burner, ~ ,small~ quantities ~ of roll sulfur, -iphoqihorus, acetone, ether, carbon d~sulfide,gasoT
which sulfur, red phosphorus, and ether catch on fire. Continue heating the rod testmg the acetone and gasoline at intervals, until the glass glows and the rod bends in the flame. Immerse the rod 1x1 each fuel causing it to boil. Finally ignite the fuels with a match.
EMONSTRATION
bt ~atchglasses ill a row on the desk top and place ?of tlw combustible materials In each. Slightly warm \gh+ rod in the flame and touch to each material 11ur1i Carbnii d~sulfide ignites. R a s e the tempera?of the rod by small increments not~ngthe order ill
WARATIONOF WHITE PHOSPHORUS FROM PHOSPHORUS
REMARKS
Few students antic~patethat sulfur will ~giiitebefore red phosphorus and that gasoline is so d~ffieultto ignite. The hazardous nature of va+ion diwlfide is amply emphasized.
(A t k e l~d
I
~ h t l r dby: ,Tacoh Brodkin, Plainview High School, Xew Yorli %id hj: C. T i . AIcCarty, Michigan State University, East Lanmg
RIPARA
!~I>IAIII two dry l'yre~test tuhes, one 6-inch and one h h To the 8-inch test tube add 0.25 g red phosh r u q Fill the 6-inch test tube full of cold water, theouts~de,and insert it into the larger tube. The hot t11r smaller test tube will be supported hy the r d of the larger tube.
Hmt [he red phosphorus in the larger tube unt11 a bp~tappears on the cold surface of the inner tube.
Allow to cool. Upon removal of the smaller tube the white phosphorus on the bottom mill ignite. REMARKS
This demonstration is useful in connect~onwith the discussinn of energy of formation of substances After discussion the class may conclude that x h ~ t phosphorus c has in some way stored the energy TT hich brings it close to that required to mitiate a self-susta~ningreact1011 with oxygen Energy has been added to the phosphorus in converting it from the red to the vhite form.
