LETTERS
DEMON STRATION INVOLVING AIR PRESSURE G. M. LISK Northwestern State College, Alva, Oklahoma
THE absorption of ammonia in water may be demonstrated by the apparatus in Figure 1. The ammonia is prepared by boiling concentrated ammonium hydroxide and passing the gas through Drierite. Upon pressing the bulb of the medicine dropper, the balloon swells. Shaking the flask hastens the action. HCl gas may be used instead of NHa.
Another Mnemonic To the Editor: H. H. Hatt's letter in the April, 1941, issue of the JOURNAL OF CHEMICAL EDUCATION concerning a rule for remembering that caproic, caprylic, and capric acids constitute the sixth, eighth, and tenth members, respectively, of the fatty acid series reminded me of this mnemonic which I used when I was in college to remember the names of the first eleven normal fatty acids containing an even number of carbon atoms. The trivial names of all the normal fatty acids with an even number of carbon atoms, from acetic acid through stearic acid, begin with letters which occur in normal alphabetical sequence, as may be seen from the list below: 1. 2. 3. 4.
5. 6. 7. 8.
TOY BALLOON
Cs C4 Ca CB Clo CIS CM
Acetic Butyric Caproic Caprylic Capric Lauric Myristic Palmitic
Ce
The two acids immediately following stearic acid in the above series are Arachidic, Czo,and Behenic, Gz, in the order named, and here again the initial letters of the trivial names fall in the sequence of the alphabet. If Oleic acid, with its sixteen carbon atoms, belonged to the above series it, too;-bould fall in alphabetical order just Hfter Myristic acid and just before Palmitic. acid. W. T. SUMERFORD SCHOOL OF PHARMACY GEORGIA ATHENS,GEORGIA
UNIVERSITY OR
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Large Crystals
The creation of a vacuum when steam is condensed may be illustrated by the same apparatus. Boil a little water in the open flask; remove the burner; insert the stopper carrying the medicine dropper and balloon. Press the bulb, and as the steam condenses, the balloon swells. Action of an air pump may also be demonstrated by replacing the medicine dropper by a length of glass tubing attached to an air pump.
T o the Editor: The recurring appearance of articles on the growing of chrome alum crystals suggests that some of your readers might be interested in a note regarding the following procedure, which I cannot recall seeing written up anywhere. Large crystals which require no protective coating may be grown in solutions containing approximately equal weights of potassium chrome and potassium aluminum alums. I have had one about three inches in diameter on my desk for six years without noticeable efflorescence. The depth of color of such crystals may be varied by changing the amount of chrome alum in SUMMER CHANGE OF ADDRESS solution, piving a good demonstration of the formation UNTIL September 5, all correspondence for the of solidsolutions. R. P. SEWARD Editorial Officeof the JOURNAL should be addressed to: JOURNAL OF CHEMICAL EDUCATION, WOODS HOLE, PENNSYLVANIA STATE COLLEGE STATE COLLEGE, PENNSYLVANIA MASSACHUSETTS. 346
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