Laboratory bench
A properly designed laboratory bench is one of the most important elements of safe and effective laboratory practice for low vision students. The laboratory bench pictured below was designed by Dr. Lillian Rankel at Hopewell Valley Central High School.
A disposable plastic syringe (below left) is modified by cutting notches along the plunger. This allows the student to feel where to stop when filling the syringe. Syringes between 1 mL and 20 mL volume can be used. This technique is ideal for delivering small volumes with high precision. This is used in the experiment "Balanced Chemical Reactions" in the Prentice-Hall Chemistry Laboratory Manual (formerly the Addison-Wesley manual).
A float device (above right) allows for measurement of larger volumes by using a graduated cylinder. The float is cut to the appropriate diameter for the graduated cylinder. A Styrofoam disk is fitted on the end of a wooden dowel rod. The dowel rod is then marked every 5 mL for a 25 mL graduated cylinder. The tick marks are then marked with a bead of hot glue. After liquid is added to the cylinder, the floater is placed inside. By gently feeling which dot lines up with the top of the cylinder and counting the number of dots, one can determine the volume of liquid.
Hand held submersible audible light sensor
Please click to download the manual for using the SALS in PDF or Microsoft Word format.
Talking Tools for Physics Experiments
Some of the materials presented here are based upon work supported by the National Science Foundation under grants HRD-0435656 and HRD-0726417. Any opinions, findings and conclusions or recommendations expressed in these materials are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
In this picture, the bench is set up for an acid-base titration. A Vernier drop counter, pH electrode and buret are on the right side of the bench above a magnetic stir plate. In front of the stir plate and to the right is a balance that is connected to a laptop computer. In front of the computer on the left side of the lab bench is the ILAB Submersible Audible Light Sensor (SALS) probe. To the far left is a green waste container and a roll of paper towels on the rod to the ring stand. The ring stand poles have a brightly colored tennis ball on top as a visual cue and to prevent injury. A flat container (not shown) holds a variety of notched, Braille labeled syringes.
The SALS can be used to measure the amount of liquid in the buret. The SALS probe is moved slowly up the side of the buret and the pitch changes when it crosses the liquid meniscus. This allows the student to add liquid to the buret without overfilling. The SALS can also detect the titration endpoint if an indicator such as thymolphthalein is used.
Volumetric syringes
Measuring larger volumes in a graduated cylinder
We have recently completed a simple hand-held, submersible audible light sensor (SALS). Unlike the color sensors, the SALS provides readings of light levels in real time. It is therefore ideal for following chemical changes as they occur. The sensor fits inside a test tube and is also compatible with other standard glassware. The design, prototyping, and testing of the first prototype sensor were carried out by a team of undergraduate engineering students at Penn State as a senior design project. The second generation sensor was designed and is now being produced in the Chemistry Electronics Shop at Penn State.
Click to download a paper in Assistive Technology Outcomes and Benefits describing the use of the SALS.
This device can indicate a change in color of a solution, and can also detect the formation of a precipitate in a test tube in real time. The light sensor is a glass wand with a photodetector inside the tip. Typically, the sensor is used by placing the test tube or flask on top of a light box, as illustrated above in the "Clock Reaction" experiment in the Prentice-Hall Chemistry Laboratory Manual. The current in the light sensor is converted to an audible pitch by an external control box. The darker the solution, the less light is detected, and thus the pitch is lower. This sensor can also detect the formation of precipitates. If two solutions are mixed and a precipitate is formed, the pitch is lowered by scattering and blocking of light by the particles.
The box that controls the probe is shown above at the right. The top switch turns the device on and off. To hear the tone corresponding to the current light level, the first button is held down. This button is Braille-labeled 'play'. In order to hear a high reference tone the second button is held down. This is labeled 'hi'. The third button is pressed to hear a low reference note. This is labeled 'lo'. The high and low reference pitches gives the user an understanding of the range. The fourth button allows the user to store a tone. By pushing this button and the three buttons at the bottom (memory A, B, and C) at the same time, the controller will save the current tone. The user can come back to that particular tone by pressing one of the memory buttons. The black knob in the lower right corner is used to control the volume. The controller is battery-powered and can be kept on the lab bench or worn on a belt.
The light sensor can detect a color change associated with a change in pH. Its use in the experiment 'Estimation of pH' in the Prentice-Hall Chemistry Laboratory Manual is shown above at the right. The change in the color of an indicator produces a change in the pitch. This is demonstrated above with phenolphthalein as the indicator. The change from colorless to pink and the corresponding lower pitch indicate that the solution in basic. Use the "Experiments" tab at the left to download a movie showing the use of the SALS in the iodine clock reaction.
Color identifiers
The Color Analysis Laboratory Sensor
(CALS) is an inexpensive color recognizer that was developed in the Chemistry Electronics Shop at Penn State. The CALS consists of a hand-held probe connected to a digital controller box. The CALS reports the color of a solid object or surface (e.g., a powder in the chemistry laboratory, a piece of fabric, or color in a picture) to the user. Before use, the sensor is calibrated by holding the probe up to a piece of white paper. The probe is then held above the test object (e.g., a powder, a sheet of colored paper, or a colored liquid), and the controller box speaks the color. The user can also choose to have the CALS report the color numerically as a series of red, green, blue (RGB) and white color values.
The hand-held probe for the CALS is not intended for use in solutions because the probe is not submersible, and because reflected light from glassware can give an inaccurate color reading. The CALS will reliably report the colors of solutions in a standard test tube by using the liquids probe, an attachment that plugs into the same jack on the sensor box. In this case, light is transmitted directly through the solution in the test tube rather than reflecting back to the probe.
The SALS and CALS are not yet commercially available products, but are used by students and educators who are part of the ILAB project. Please use the "Contact" tab at the left if you would like to find out about using these devices in your classroom.
The Mobile Speak Plus color recognition software sold by Code Factory is used on this cellular phone to tell the user the color of a solid compound or a solution. The software needs occasional calibration by taking a photo of a white piece of paper. (Shadows can lead to inaccurate readings). Holding the phone a few inches away, the student snaps the photo and an audible reading of the color is announced. The software also gives a confidence reading of high, medium, or low.
Two versatile talking tools that can be used in Physics as well as Chemistry courses are the Talking Stopwatch and the Talking Voltmeter.
These tools have been designed with controls that are similar to those of the SALS and CALS, so that mastering their use is simple after becoming familiar with any one of the tools. The image below shows the Braille-labeled talking stopwatch, which can provide timing with an accuracy of 0.01 s. The functions of the stopwatch (start, stop, reset) can be actuated with Braille-labeled buttons or by using electrical inputs from an external device, such as a photodetector.
