LIVE CHEMISTRY 617

LIVE CHEMISTRY.By H. R. SMITH,

La^ View High School.

We are much encouraged in this work by the number of contributionsrecently sent in, and also by the appreciative words of teachers who arefinding value in the published experiments. We ask again for helpfulsuggestions and criticism from anyone interested in this work.You can do much study on foods with profit at this time of the year.

The Pure Food Laws are slowly improving conditions for the productionand .sale of food products. Foods are of better average quality thanthey were ten years ago. The public needs to be better informed onfood quality and more critical in comparing real quality with the advertisedquality. A little effort in the chemistry classes will help the cause greatly.Have you found out what your State Food Commission is doing? TheIllinois Commission will deliver free illustrated lectures in Illinois on"Labels and Their Meaning," "Food Sanitation," "Milk: Its Care andDangers," "Flies and Their Relation to Disease." The last two are ar-ranged for motion pictures.The Chemistry Section of the Central Association of Science and

Mathematics Teachers, under the direction of S. R. Powers of TerreHaute, Ind., is preparing a survey of methods and conditions of teachingchemistry in the Central states. Such a survey forecasts a general im-provement in the teaching of the subject. We trust that it may berealized; and it will, if teachers will respond. The list of questions areneatly typed in pamphlet form at some length, but the questions are soworded that the answers may be brief. We urge that all teachers ofChemistry answer the questions and send them in, in order that the workmay be most fruitful. If you do not receive a copy, ask Mr. Powers forone.

RECEIPT FOR HOMEMADE BAKING POWDER.To be Done Outside and Results Compared in Class.

i Ib. cream of tartar.i Ib. baking soda.1 tablespoon cornstarch. Sift six times and keep in an airtight can.Using the above receipt, compare the price of baking powder ’made at

home and that bought at the grocer’s. Tell which you would prefer, touse and give reasons.How much cream of tartar would you need to use with one pound of

baking soda?When this baking powder is used, how much Rochelle salts would be

formed?How much ’carbon dioxide would be given off?In using baking soda, would you use sweet or sour ’milk? Why?In using baking powder, would you use sweet or sour milk? Why?How does carbon dioxide cause cake to rise?What determines the amount of soda one must use in baking a cake?What kinds of baking powder are there beside the cream of tartar

baking powder?ALICE M. CHILD,

East Division High School, Milwaukee, Wis.

A LIVE STUDENT.In the department of Live Chemistry in SCHOOL SCIENCE AND MATHE-

MATICS for June, 1914, we briefly outlined a method for making a

618 - SCHOOL SCIENCE AND MATHEMATICS

souvenir stick-pin from a silver coin. A student in our laboratory hasextended the experiment to another metal. While visiting at the homeof his uncle a few weeks ago, he noticed an old ’watch case in the rubbishheap. Thinking that the case might contain some gold, he brought it tothe chemical laboratory, and placed it in dilute nitric acid. The porousmass that did not dissolve, he rightly concluded to be gold. He placedthis on a piece of charcoal, added a little borax, and in a few minutes,with the blast lamp, he had a beautiful gold bead. For twenty-five cents,a local jeweler inserted a gold-plated stick pin and the result is a solidgold article of jewelry, worth possibly somewhere between five and tendollars. Other students have since been looking into rubbish heaps andbarrels for old watch cases and cast-off jewelry, and that is the reasonfor offering this paragraph to the Editor of Live Chemistry.

NICHOLAS KNIGHT,Cornell Colleger Iowa.

SOME SIMPLE ORGANIC COMPOUNDS.MATERIALS :KCaH^Os; NaOH; HC1; lime water; methyl alcohol;. piece of copper

wire 30 to 40 cm. long; resorcin solution (1%) ; cone. H2S04; sweet milk;potassium bichromate; ethyl alcohol; carbon tetrachloride (CC^).PROCEDURE.,: ’

�;< ’.i^-iT^IS(a) Marsh Gas.1. Mix about 10 g. of powdered potassium acetate with three times

its weight of soda lime. Place the mixture in a flask provided with aone-hole rubber stopper and delivery tube. Heat strongly over a wiregauze with a luminous flame. After the air is expelled, collect the gasin a test tube over ’water.

2. Thrust a burning match into the mouth of a test tube of the gas.Fi1! another tube half full of gas, raise it from the water and immediatelyapply a flame to the mouth of the tube. Complete the equation: CH^+202->?+?. , , i il-MKffI

3. Place some of the material remaining in the flask used as a generatorin a test tube and test it for the presence of carbonates by adding HC1and allowing the gas generated to bubble through lime water. Completethe equation:

2KQH30d-2’NaOH-» ?+?+ ?,

(b) Carbon Tetrachlorid.1. Moisten a filter paper with five cc. of alcohol or kerosene. Place

in a crucible and ignite. Pour over the flame 1-2 cc. of carbon tetrachlorid.Explain what causes the flame to be extinguished. Warm 2 cc. of carbontetrachlorid in a deep clay crucible. Lower a lighted candle or a burningsplinter of wood into the fumes. Explain the result.How is CCli related to marsh gas? It is used in ’cleaning and in dis-

solving fats and oils instead of gasoline or benzine. Why?(c) Formaldehyde.1. Cut a piece of heavy copper wire about 40 cm. long. Twist half

the length of the wire into a close spiral around a lead pencil. Mix 2cc. of wood alcohol with about five times the amount of water. Placethe mixture in a test tube and stand the tube in a beaker of cold water inorder to keep the contents cool while the reaction takes place. Heat thecopper spiral strongly in the upper Bunsen flame. When it reaches a redheat, thrust it quickly into the tube of dilute alcohol. Remove the spiral,dip it into some cold water, and then repeat the whole process five orsix-times. What change takes place in the copper spiral while it is heldin the oxidizing flame? Complete these equations and explain: