dltd by,
WALTER A. WOLF Cdgmte University
Hamilton, New York
The Recovery of Silver from Film
H. Nechamkin and P. E. Dumas Trenton State College Trenton, N.J. 08625 The increased current interest in silver, gold, and other metals is sufficient reason for having students perform experiments that illustrate their chemistry. The following experiment is an example of silver recovery. Weigh about 3 g of film cut into small pieces and place them into a small porcelain crucible. Heat in the hood a t red heat for 5 min. Add to the ash in the crucible about 5 ml of 1:l. HN03:HzO and boil gently. Filter and collect the acid extract in a test tuhe. Slowly add 5% NaOH solution to the test tube until a dark brown prec i ~ i t a t eawwears. and then add dilute HNO?-droowise until . dissolves. The solution now contains AgN03 the in sliehtlv " .acid medium. Add a 2-3-in. length of copper wire to the solution and allow to stand a t least overnieht. The disolacement reaction beeins " immediately hut requires time to approach completion. Remove the wire, and collect the precipitated silver on a filter. The collected silver may he gently hammered to obtain a silvery lump of the metal.
Field Trips as a Supplement to Science Major General Chemistry Laboratory J i m m y C. Stokes ~illiam L. Loekhart and Latha M. Barnes West Georgia College Carrollton, Georgia 30117 The use of field trips in sciencemajor general chemistry is not common. We have found that most general chemistry students have very little, if any, conception of what a nonacademic laboratory operation looks like and how it functions. As a part of the second quarter general chemistry laboratory, we require students to complete three field trips in addition to five "wet" labs. We ~enerallyarrange to have six or more possible experiences in t h e space of thequarter and allow the students to register for trips that appeal to them individually and those that might be useful in their eventual professional life. The most popular of the field trips have been visits to the state crime laboratory, a local copper refinery, and a local hospital laboratory. We have also visited water treatment plants, sewage disposal operations, metallurgical laboratories, and federal laboratories, such as the Center for Disease Control. We have found local and area industries and laboratories verv rece~tiveto student visits. Seminars and iourual ahstractingire available for students that have drfficulty arranging three actual field trips. The attitudes of students on 370 / Journal of Chemical Education
returning from the field trips have encouraged us to become more and more involved in making potentiai scientists aware of what they should realistically expect from a career in science. ~ u r t h e information r is available from the author on request.
A Low Cost Colorimeter Glenn A. S t a h l and Mamie Moy Uniuersity of Houston Houston, Texas 77004 We have constructed a colorimeter consisting of a 10 X 8 X 5-in. wooden box made of flat black, %-in. plywood. A double partition of %-in. plywood divides the box into two main compartments. One compartment houses the light source, and the other comwartment is subdivided into 3 sections-(1), , storage, (2) sample cell and detector, and (3) electronics. The douhle portion has a l-in. hole drilled in its center which allows light to pass to the sample cell and detector section. Double partitioning cuts down on stray light and serves as a holder for clear colored plastic filters. An 8 X 10-in. lid of %-in. plywood is a sufficient light harrier when covered with black felt. The light source is any conventional size incandescent lamp and rubber socket. The samwle cell is a test tube held unrieht by a drilled wooden block. be detector, a Radio Shack ~ r & e r 276-115 photocell, is glued on a piece of plywood, and placed behind the sample cell. The photocell has a wide spectral response curve in the visible spectrum with maximum 0.5 V and 60 PA current output. When placed in series with a l - K potentiometer and Simpson SK525-495 D-50 microammeter, the student can place a solvent-filled sample cell in the instrument.. .~ l -u in a the light source. and adiust the meter to maximum output, or 10096. In succ&sive s A p l e s the student inserts the next sample test tuhe and records the readine of the microammeter. The colorimeter has been used hv nursing. -. nutrition, hotel and restaurant, and other nonsciince majors to determine ferrithiocyanate ion equilibrium constant, persulfate ioniodide ion rate constant, and to demonstrate Beer's Law. A drawing of the apparatus is available upon request.
Compact Compact Joseph A. Solomon of the Philadelphia College of Pharmacy and Science reports the following procedure allows the rapid and safe preparation of dilute sulfuric acid in the lahoratory. Tare or weigh a large beaker on a top-loading balance, Add a quantity of ice made from distilled water. Weigh the ice and add 1 ml of acid per gram of ice. The heat of fusion of ice permits the addition of acid to he as rapid as one can pour it over the ice. The heat released is just sufficient to melt the ice with the resulting solution being barely warm. This procedure reduces the danger and the time consumed by the normal dilution methods.
