VOL.3, NO.5
GETTING OFF AT BALYIMOR~
671
GETTING OFF AT BALTIMORE CHARLES H. STONE. ENGLISH HIGHScnnn~.BOSTON, MASSACAUSE~S
When you are journeying from Philadelphia to Washington on important business, i t is logical to remain on the train until you arrive a t your destination; you do not get off a t Baltimore. But in many of our schools we are often permitting such arrangements of laboratory procedure that our students "get off a t Baltimore" instead of continuing to the end of their journey. For example, we start Johnny on an interesting trip via the hydrogen route. He sets up his apparatus, puts zinc into the generator, pours in sulfuric acid, and collects the hydrogen produced. He observes the physical properties of the gas, tests i t for its chemical properties, writes a record of his work including one or two equations, answers such questions as we may find time to ask him and the experiment is concluded. If he has avoided blowing himself up by a premature ignition of the hydrogen as it escapes from fhe generator, we send up a prayer of thanksgiving and start him on the next experiment which may be concerned with distillation or some other topic. Right there we are letting him "get off a t Baltimore." Is there any reason why he should "get off" there? Is i t not important he should have something more than a theoretical knowledge of the fact that when zinc acts on sulfuric acid there is another product beside hydrogen? Is there any reason why we should let Johnny's opportunity for obtaining this product byfiltration,evaporation,andcrystallizationpass? Won't Johnny have a much clearer idea of what really takes place when metal and acid interact if he prepares the secondary product? Will he ever forget the astonishing difference between the anhydrous and the crystalline forms of zinc sulfate if he has once prepared them himself? Why should we permit or require him to leave off his experimental work on a certain topic before it has been brought to a logical conclusion? Over and over, teachers do this in the laboratory. How many of us have our students recover the potassium chloride and manganese dioxide from used "oxygen mixture?" How many of us have them recover the secondary product formed by the interaction of ferrous sulfide and sulfuric acid by filtering and crystallizing the ferrous sulfate? How many of us have them recover the calcium chloride formed when marble and hydrochloric acid are used to prepare carbon dioxide? And so on through the year. If we can go a step farther and show a use for the recovered product so much the better. A little of Johnny's recovered manganese dioxide dropped into some fresh hydrogen peroxide will show by the liberation of oxygen that the catalytic power has not been lost through its first use with potassium chlorate. Ink can be made from Johnny's recovered copperas,
and he will be "tickled to death" to make some. His recovered calcium chloride will show that it is deliquescent if left for a day or two in a dry dish. Other examples are not far to seek. The product left after preparing acetylene will yield some lime water if filtered; it will give a test for a base with phenolphthalein; and the dried residue will give a most satisfactory yield of ammonia if rubbed with a little of any ammonium salt. The copper nitrate liquid left from the preparation of nitric oxide will yield some fine copper oxide if evaporated to dryness with strong heat, and this oxide in turn will yield copper if reduced with hydrogen, thus getting back to the original metal with which the experiment was begun. The field is limitless for this sort of work and it is work that is worthwhile. Are you letting your students "get off a t Baltimore?"
