Microlab’s Universal Sensors

Identified by this image of the Andromeda galaxy, MicroLab’s family of Universal Sensors

open new opportunities for students. They are unique, rugged, precise, and compatible with

all of the common brands of educational data acquisition systems. They will have a long useful

service life, and are so affordable that you can purchase them from your supply budget.

Your students will ...

Atoms First

An “Atoms First” course organization creates a vacant spot early in the

general chemistry lab curriculum. Faculty are discussing light, atomic spec-

tra, electron structure, and bonding. Students are not yet ready for tradi-

tional “wet chemistry” lab topics.

Here are some tools to help fill this vacuum with colorful, interesting and

interactive “hands-on” experiments: The Energy of Light and Planck’s Con-

stant; atomic emission and molecular absorption spectra; and hydrogen

spectra and the Bohr electron model. Because data is quickly captured,

most student time in these experiments is spent with graphical analysis

with Excel and Image j . One set of equipment can serve two lab groups.

Software is included.

Acid-Base Chemistry

Titration curves provide a lot more information about an acid-base

system than an indicator end point titration. Students encounter

buffer regions and Ka, learn to choose indicators, and learn to use

derivative plots to identify end points.

MicroLab’s Model 154 Constant Volume Drop Dispenser eliminates

pressure head variation and provides industrial needle valve con-

trol of flow rate, which is linear with a correlation factor of 0.9999.

Our patented Model 226 IR Reflective Drop Counter solves align-

ment problems with front surface reflection, and compensates for

both changes in room light and drop fragmentation. Both units are

basically unbreakable.

Electrochemistry

Electrochemistry is somewhat of a step-child in the general chemistry

curriculum. Often left for quick treatment at the end of the semester,

“hands-on” electrochemistry labs are thought difficult and expensive.

This need not be true. Here are some new tools that will make electro-

chemistry understandable, affordable, and easy and fun to teach. Oxi-

dation-Reduction / Electroplating / Half-cells / Electrochemical Series /

Nernst Equation.

MicroLab’s Universal Sensors

MicroLab, Inc. • microlabinfo.com • (888) 586-3274 • P.O. Box 7358, Bozeman, MT 59715

• Improve their data quality • Better visualize relationships in data • Use smaller, safer, “green” samples. • Expand their lab content •

Atoms First

The Energy of Light – Planck’s Constant Students use MicroLab’s Model 214 Energy of Light Module to visualize, quan-

tify, and understand the relationship between energy, color, wavelength, and

frequency of light. They do this by easily measuring the voltage required to

initiate emission of light in a series of visible and IR Light-Emitting Diodes (the

band-gap energy).

This relationship between energy and color/wavelength/frequency of light can

be demonstrated at four different conceptual levels, depending on the level of

the course.

• The energy of light increases as color changes from infra-red to violet. UV

has enough energy to break chemical bonds and to cause sunburn.

• The energy of light is inversely proportional to the wavelength of the light

wave.

• The energy of light is directly proportional to the frequency of the light

wave.

• The mathematical proportionality between energy (E) and frequency (ν) of

light is known as Planck’s Constant (h) : E = hν.

MicroLab’s Model 214 Energy of Light apparatus can be used “stand-alone”

without a MicroLab FS-528. In this operating mode, an inexpensive digital

voltmeter (DVM) is used as the readout device. Power is supplied by a small

plug-in wall power pack to eliminate the need for batteries. Excel software

(illustrated) is provided for data analysis and presentation.

MicroLab’s Visual Spectrometer: Atomic and Molecular Spectra Measurement of atomic emission spectra is the foundation

on which our understanding of the electronic structure of

atoms is built.

Would you like your students to …

• Understand atomic emission spectra? How about Ab-

sorbance, and how to choose an analytical wavelength

for a Beer’s Law experiment?

• See real emission and absorption spectra in full color?

• Learn to quickly calibrate a spectrometer using a known spectral source, and then use this calibration graph and equation to identify

unknown spectral lines with an accuracy of about 1 nm?

• Have a 1000+ channel visible region diode array spectrophotometer with 1 nm accuracy and 4 nm

FWHM available for each of your students?

Would you like to pay less than $200 for this instrument?

Check out MicroLab’s new patented Model 141 Visual Spectrometer. It is rugged, affordable and easy-

to-use. Couple it with a our Model 243 web camera, a point-and-shoot or cell phone camera and the

included fiber optic adapter to bring in a known reference spectrum, and you have a powerful cali-

brated emission spectrophotometer. (Hg reference on the previous page.)

Use it with MicroLab’s FS-528 FASTspec™ scanning spectrophotometer, and students will bridge the gap

between visual observation and quantitative measurement of color and absorbance.

Data analysis is provided by powerful image analysis software.

Image J is a photographic pixel density analysis program developed for

life-sciences researchers by the National Institutes of Health. It is avail-

able free on the NIH web site http://rsbweb.nih.gov/ij. . Image J is

extremely easy to use – in this application the student just draws a box

around the spectrum of interest, clicks the mouse, and the intensity

profile of the spectrum is calculated and displayed.

Model 243 Web Camera and Spectrometer mount.

Model 141 Visual Spectrometer + fiber optic cable.

Acid-Base Chemistry The most common use of titrations is quantitative: How much of the analyte is present?

This usually involves an equivalence-point / indicator titration. There is a lot more infor-

mation available if one is able to track and plot pH, temperature, conductance, or other

solution properties with respect to volume . Examples include ...

• The difference between strong and weak acid titrations with strong base

• Choosing chemical indicators

• Buffer regions

• Calculation of pKa

• Use of derivative plots to accurately locate end-points.

None of these concepts can be developed easily with manual titrations.

Drop counters and an accurate drop dispenser are a useful and cost-effective alternative

to burettes. They will not break and their resolution is about 50% better. And they do not

get tired or distracted. A drop counter is calibrated by counting the number of drops re-

quired to fill a 10.00 mL graduated cylinder.

MicroLab’s patented Model 226 Drop Counter uses a reflective infra-red sensor that

counts by catching front surface reflection from each drop. This scattered light makes

alignment non-critical; the sensitive volume is a sphere about 1 cm in diameter. A back-

ground correction circuit measures and subtracts background light 800 times each sec-

ond, making the unit essentially immune to changes in room lighting. An internal circuit

inserts a 25 millisecond “dead time” at the detection of each drop, eliminating false

counts from fragmented drops. Although this limits the maximum count rate to about 40

drops per second, it is not of concern because aqueous drops coalesce into a stream at

about eight drops per second. LED indicators show power (green) and counts (red).

More important to accurate results are stir rate and solution mixing, the response time of

the pH electrode (close to one second), and the reaction rate of the compounds involved.

Strong acids react more quickly than weak acids. The result is that, if the drops are closer

together than about 1.5 seconds, the pH reading does not reflect the true chemistry going

on in the solution.

Accurately counting drops is only half of the task. Equally important is a source of repeata-

ble, constant volume drops. Because of its large pressure head change during a titration

and relatively large drop size (0.05 mL), a burette is a poor choice for a drop dispenser.

Both drop size and drop rate are dependent on a drop dispenser’s pressure head. Micro-

Lab’s new precision Model 154 Constant Volume Drop Dispenser has a 50 mL titrant reser-

voir and will deliver 30 mL with a 1 cm change in pressure head - about 3% that of a bu-

rette. Drop rate is easily controlled by an industrial multi-turn needle valve, and a stopcock

controls on/off after drop rate is set. Drop volume is about 0.034 mL, and a drop volume /

drop count graph is linear with five 9’s in its correlation coefficient.

Drop Counter compatibility: Vernier: Requires Lab Pro Digital Adapter, DG-BTD, $5. Pasco: MicroLab 226 drop counter 1/4” stereo phone plug connects to Pasco photogate / radiation counter input. For Science Work-shop, use Pasco Digital Adapter PS-2159, $59.

Model 226 IR Reflective Drop Counter

Model 154 Constant Volume

Drop Dispenser

Electrochemistry

● Oxidation – Reduction

● Electroplating

MicroLab’s inexpensive Model 232 Electroplating Module provides three

volts DC battery power from two AA batteries, and a lamp to monitor elec-

tron flow in basic electroplating experiments. Students can observe oxida-

tion and reduction in “real time” as copper is deposited on a key or other

metal sample. Alligator clip leads included.

● Half Cell Reactions

● The Electrochemical Series

● The Nernst Equation

MicroLab’s Model 152 Mult-EChem Half Cell Module has space

for eight metal/ion electrochemical half cells, each equally ac-

cessing a central aqueous salt bridge through a replaceable

porous cylinder. Small (3 mL) samples and the aqueous salt

bridge provide extremely stable electrochemical cell voltage

measurements (± 1 mV / 30 minutes) with a lab data acquisition

system or an inexpensive digital voltmeter. The Model 151 Met-

als Kit provides 5 cm metal samples of Ag, Al, Cu, Fe, Ni, Pb, Zn,

plus sandpaper to clean samples and Cu foil for electroplating

experiments.

Getting Started in Electrochemistry

Because many of us work with limited equipment funds, or would like to explore a

new lab topic before investing much in equipment, here’s how the five introducto-

ry topics illustrated above can be demonstrated and taught with inexpensive appa-

ratus.

Exploration of concepts of oxidation, reduction, and electroplating require only a

battery, a flashlight bulb to monitor current, two clip leads, and some copper wire

and copper sulfate. The Model 232 Electrochemistry Module provides battery,

bulb, and clip leads. The electrochemical series may be developed experimentally

using small, safe, low-cost chemical samples using our inexpensive Model 152 half-

cell module, the Model 151 Seven-metal kit, and a common digital voltmeter. The

Nernst Equation’s prediction of change in cell voltage with changing ion concentra-

tion may be demonstrated by holding one half cell ion concentration constant and

changing the other by powers of ten (Ag+ data to the left). Note that the slope is

59 mv / decade, as predicted by the Nernst Equation constant RT/nF, concentration

expressed with base 10 logs.

Voltmeter compatibility: Compatible with Pasco or Verner data acquisition systems with ± 10 volt DC volt-

age input lead. Compatible with MicroLab data acquisition systems ± 2.5 volt DC or ± 10 volt input.

Compatible with any digital voltmeter (DVM); set to ± 2 or ± 20 volt DC range.

July 22, 2016

0.5080.448

0.388

y = 0.0598x + 0.56760.3

0.4

0.5

0.6

-4 -3 -2 -1 0

Vo

lta

ge

vs

Cu

R

efe

ren

ce

Log [Ag+] Concentration

[Ag +] Half Cell Concentration

Model 232 Electrochemistry Module

Model 151 Metals Kit

Model 152 Half-Cell Module

Incr

easi

ng

attra

ctio

n f

or

elec

tro

ns