1

Viktor Obendrauf
University of Graz, Institute of ChemistryA-8010 Graz, Schubertstraße 1e-mail: viktor@obendrauf.com
MORE SMALL SCALE HANDS ON EXPERIMENTS FOR EASIER TEACHING
AND LEARNING„A pretty experiment is in itself often more valuable than twenty formulae extracted from ourminds. Albert Einstein (1879-1955)
Neurobiological research proves that lasting learning is closely linked to emotions. A ‚pretty’reaction arouses emotions just like a dangerous or a dangerous looking experiment.
Many colleagues can confirm that most of the students remember nothing better than‚beautiful‘ or ‚dangerous‘ experiments. Through aesthetically arranged and really exciting
experiments they frequently grasp the associated theoretical concepts more easily.
Of course, definitely dangerous experiments must be cancelled in school. Chemical education
should be as safe as possible for teachers and students. But chemical demonstrations which
are classified as possibly dangerous by the students can support learning with emotions. Using
microscale techniques many potentially dangerous reactions can be performed in a safe andinexpensive way.
There exists no scientific definition for aesthetic science phenomena. But there exists a
general consensus that chemical demonstrations and students activities can be designed moreor less pretty. Classical examples of aesthetic reactions and/or aesthetically presented
processes are various coloured structures and crystallisations in Petri dishes, projection
cuvettes and on microscope slides. For many people pyrotechnic effects are beautiful. Even
the burning down of a simple ice candle can create emotions. Many burning ice candles
arranged as pyrotechnic numbers and letters are much more than a simple reaction between
heated titane particles with oxygen of the air.
For many students, unclear experimental arrangements are not elegant or even beautiful. They
want to pick up the experiment and the concepts behind it as fast as possible. A simple andclear experimental procedure without many fixing stands and clamps, that is focused on a
microscale level and enlarged with modern electronic equipment for large auditoriums, cansometimes improve both the aesthetics and safety of potentially dangerous experiments.
For many teachers and lecturers, experimental procedures are not elegant and pretty when
they require expensive and time-consuming preparations and exhausting clean ups with lots ofwaste. Going microscale can improve the aesthetics and the safety of chemical reactions by
reducing the time, costs and waste.
Six years ago it was a big honour and also a great pleasure for me to be invited to give aplenary lecture during the 16th ICCE in Budapest dealing with small scale and microscale gas
reactions. The audience agreed that special video techniques can be very useful for
performing time-saving and cost-saving small scale reactions in big lecture-theatres without
polluting the environment. By enlarging the improvised low-cost-equipment with modern
digital video projection techniques the properties of very poisonous gases can be safely
demonstrated without a fumehood. The experimental topics during the lecture in Budapest
were: the generation of chlorine, acetylene, hydrogen, hydrogen sulphide, sulphur dioxide,ammonia and oxygen, the reactions between sodium and chlorine, hydrogen and chlorine,
chlorine and acetylene, hydrogen and oxygen, hydrogen sulphide and sulphur dioxide.

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The same low cost equipment and digital video techniques — enriched with some special
products from any European supermarket and a couple of improved ideas to generate, storeand dispose small amounts of hazardous gases — should be used for the lecture in Seoul.
In any case, the discussed small scale experiments are not designed for combination withvideo techniques. For normal classrooms, the philosophy is that a badly arranged experimentin a fumehood or behind a safety shield is less impressive for creating emotions than a small
scale portable apparatus which needs no fixing stands and allows the lecturer to perform andrepeat the experiments closer to the students.
Detailed instructions and figures dealing with the special materials necessary for these low
cost gas generations and small scale gas reactions are described in the book of abstracts of the
16th ICCE 2000 in Hungary. These materials have successfully been used for more than ten
years in Europe and should be described again for those colleagues and teachers in Asia whohave had no chance to pick up these experimental suggestions until now.
Material © for the low cost gas generation and gas reactions [1,2,3]:(a) 1 test-tube Schott Fiolax® 16/160 mm, bulged mouth.
In this test tube the gases are generated. The rather thin but fireproof
material heats up the substances inside in a very short time; if it isnecessary, this substance can be cooled down again in a water bath orwith tap water in a few seconds.
(b) 1 soft rubber-stopper (Verneret18D) with 1 or 2 syringe needles (1.2/40 mm)
pierced through the stopper as shown in figure 1.
Figure 1
The tips of the needles in the stopper must be cut off as shown inpicture 2. The blunt needles in the stopper work as micro steel tubes
with luer connections. Needles without tips are no longer needles.
Even with differently strong acids, the stopper works for many months
without having to replace the tubes.
(c) 1 disposable syringe 2 ml (e.g. Braun ®)This syringe is used as a dropping funnel for liquids. The plunger(without washer) must be difficult to move. For this property a roughsurface inside the syringe prepared with fine iron wool is very useful.
To suck up the needed liquid it is useful to have the chemicals in 10-20 ml narrow
mouthed bottles. As a result, even concentrated hydrochloric acid or concentrated
ammonia solution is no problem outside the fume hood. To avoid contact with the adheredchemicals after filling, the syringe must be cleaned outside with a paper towel or rinsed ina beaker with water or with tap water. Then the syringe can be placed tightly in the luer
connection steel tube of the special stopper.
(d) 1 syringe 20 ml, eccenctric luer conus (ONCE ®) This syringe is used to collect and store
the generated gas and stoichiometric mixtures. To avoid pressures that are too high in theapparatus, the plunger must be easily movable when compared to the
2ml-syringe. Therefore the washer at the end of the plunger must be
slightly greased with high boiling silicon oil.
(e) 1 10 ml syringe without a plunger, first filled with activated charcoal
granular and then closed with 1 rubber stopper with 1 syringe needle
Figure 2
in it as shown in figure 1
This device is very useful to avoid excessively hazardous gases
coming out of the gas generator when the 20 ml syringe is filled andno more gas is needed.

3(f) 20 ml disposable syringe (ONCE®) with inserted piezoelectric
Figure 3
sparker (figure 3)
This device, built from a 20 ml disposable syringe and a piezoelectric
lighter allows one to collect various explosive mixtures of gases toshow the stoichiometric reactions in the syringe directly. Constructing the device: A nail is heated in a flame, this hot nail is used
to melt a small hole in the syringe, a stereo wire with blank metalends is inserted through the hole and the connection is sealed with
hot-glue as shown in figure 3. The other end of the wire must beconnected to the piezoelectric sparker so that it works (see figure 3).
(g) Steel tubes 1.2/40 mm with luer connections (syringe needles with
cut tips). The thin steel tubes with the luer connections and the bluntend serve for jets, e.g. either a) to light hydrogen or acetylene pressed out from a syringeor b) to jet the wanted gas into a test-tube or into another syringe. The steel tubes placed
the soft rupper stoppers or serving for jets work for many months without destroying
in corrosion even in contact with concentrated acids. To avoid corrosion during storage,
the steel tubes must be rinsed inside with water and dried with air. This procedure
consumes only a couple of seconds: Using a 20 ml syringe press some water through thetubes and dry the tubes inside by sucking and pressing air through them.
(h) Steel tubes 0.8/120 mm with luer connections (syringe needles with cut tips)
The long syringe needles can be used as a reaction tube with a very big (catalyzed or not
catalyzed) surface inside e.g. to heat astoichiometric mixture of sulphur 8 ml NH3 + 10 ml O2
dioxide andoxygen or as catalyst tube for the
Pt
NOxcatalytic reaction between ammonia
and oxygen (Ostwald procedure see
figure 4) etc.
The modified and strongly heated long
Figure 4needle can also be used to decompose
gaseous compounds e.g. ammonia orfor thermolysis reactions (e.g. paraffin oil to gaseous hydrocarbons).
(i) Micro burnerPortable, with piezoelectric sparker, refillable with ligher butane, burner time not limited,size of the flame adjustable, works in each position (see figure 4)(j) 15-20 cm long pieces of insulator from a stereo wire (copper wire removed), used as thinplastic tubes(k) 100 ml disposable syringe with catheter
connection (Figure 5This syringe is used to collect, store and weighlarger amounts of gases. The catheter
connection fits to the luer connection of smaller
syringes and to the outlet of a special wine
Figure 5bottle opener which works very comfortably
with commercial chargers filled with carbon
dioxide for soda bottles or nitrous oxide forwhipped cream.

4(l) Mobile small scale ozone generator
Using a silcon tube a normal small scale
oxygen gas generator is connected to atest tube which contains a thin glass tube
filled with a salt solution (e.g.copper
sulphate). This solution is in contact
with a small high voltage device (stungun, see figure 6). The second
connection of the high voltage device
leads to a sheet of copper or brassoutside the test tube, so that discharges
can be produced from outside the test
tube to the thin glass tube inside the test
tube. Pure oxygen inside the test tube
can be converted to ozone partially.
Ozone mixed with normal oxygen canbe collected in a 20ml syringe (see fig 6)

Figure 6(m) Explosion Limits Film Can
Fuji Film Can with Cap
A Fuji® film can (with a snap cap) equipped with apiezoelectric device can be used to check the explosion
limits of very low boiling organic liquids such asDistance of theacetone or ethyl acetate. The volume of the film can is3
wire ends inside::
about 33 cm .
ca. 3 - 4 mm
A very small but accurate amount of completely
evaporated acetone or ethyl acetate should give a
mixture within the explosion limits.
Example: Explosion limits of acetone (LEL: with60 g acetone/m3 air = about 2 mg acetone/33 cm3. UEL:
310 g acetone/m3 air = 10 mg acetone/33 cm3.
1 very small drop of acetone is about 7-9 mg which
Figure 7means that 1 drop of acetone completely evaporated andmixed with the air inside the closed film can is within the
explosion limit. 2 drops or more give a mixture which is
too rich.
Piezoelectric
Special lighter fuel (not lighter gas) such as ZIPPO®
device in alighter fuel consists of octane and familiar hydrocarbons
2ml syringewith a proper vapour pressure of about 0,0147 bar so that
excess liquid in the closed film cannot produce too richmixtures. Example: The calculated amount of oxygen in
the film can is about 6,9 cm3. The volume x of thevapour in the closed film can with excess liquid in it should not be more than about 0,5
cm3. (x cm3 : 0,0147 bar = 33cm3 : 1,0147 bar) Compared to 6,9 cm3 is the mixture is
the hydrocarbon vapour near the stoichiometric mixture: HC : O2 = 0,5 : 6,9 = about 1:14.
(C8H18 + 12,5 O2 → 8 CO2 + 9 H2O). It is possible to produce many harmless explosions
in the can after replacing the air and closing the container.

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MORE EXAMPLES OF EXPERIMENTS WHICH ARE WELL KNOWN BUT ARE
NEWLY DESIGNED, SMALL SCALE AND DONE WITHIN 3-5 MINUTES:
1. Photolytic reaction between hydrogen and chlorine
The air in the chlorine gas generator is replaced bygenerating chlorine, the air in the hydrogen gas generator
is replaced by generating hydrogen. To make sure that the
flash will work with the mixture every time, the hydrogencan be cleared of hydrochloric gas. Connect the 10 ml
syringe filled with charcoal with the hydrogen gas
generator and replace the air in the charcoal by hydrogen.
Then connect the 20 ml syringe filled with 10 ml purechlorine with the luer conus connection of the charcoal
filled syringe. Add 10 ml purified hydrogen (figure 8).
The syringe with the collected gas mixture is placed
vertically using a cut needle on a foam base as a stand. If
the sheet of the flash covers the attached 20ml syringe
completely, the reaction will start every time without
removing the UV filter from the flash (see figure 8).

Figure 8

2. Generation of NOx using copper and nitric acid, properties of NO, NO2, N2O3, N2O4
After replacing the air in the gas generator thewell-greased special 20 ml syringe is used tocollect the generated NOx. A 10 ml syringe
Figure 9
without a plunger, first filled with activatedcharcoal granular and then closed with a rubber HNO3
NOx
stopper, pierced by one syringe needle,
functions as a portable fumehood, after the the
20 ml syringe has filled up with the poisonous
NOx
mixture. With the generated mixture in the 20
ml syringe the solubility of NO2 in water, theequilibrium between NO2 and N2O4, theNOformation of N2O3 and a couple of otherCu
properties of the gas mixture can be showneasily.
Using a gas generator for carbon monoxide the catalytic reaction between CO and NO to N2
and CO2 can be formed in a test tube which contains pieces of a normal car catalyst.
3. Instant chemistry: Micro-ampoules as pressure-resistant permanent preparations [4]Thick sided glass ampoules often serve as containers for liquified gases and highly evaporable
liquids. These chemical-physical „permanent preparations“ have the advantage that they
demonstrate various phenomena without spending too much time on preparation and cleaning
up. If you reduce the volume of the ampoules to a few micro-litres, the ampoules containing
various substances can be sealed, given some care and experience, without the help of aprofessional glassblower. Modern soldering torches with accurate flames make thepreparation of such micro-ampoules (2-3 mm in diameter!) a lot easier.
In spite of their thin glass the tiny tubes resist enormous pressure so that you can even sealliquified carbon dioxide or laughing gas. This makes it possible to demonstrate thephenomenon of critical temperatures of various substances in a surprisingly easy way. For
example, the critical temperature of liquified nitrous oxide, which is 36.5°C, can be reached6with the help of a hairdryer within seconds, so that the liquid inside the ampoule suddenly
disappears. After all, the corresponding critical pressure amounts to 72.6 bar. Similar
experiments can be carried out with liquified carbon dioxide (critical temperature 31.6°C,
critical pressure 73.8 bar). A
6 mm glass tube
slightcoolingends
thissimultaneity of liquid and vapor
and the liquid state is seemingly
re-formed from nothing. Liquid,gaseous and – if liquid nitrogenis available – even solid chlorine
N2 (l)
can thus be produced just as
quickly as the temperaturedependent equilibrium between
NO2 and N2O4. If the mixture
Figure 10
contains NO and NO2,the deep
blue N2O3 can be permanently
2 mm glass tube
preserved in quite a spectacular
way even at room temperature (traditionally this is only possible through cooling). Above its
melting point (-100.1°C) N2O3 decomposes according to the following equilibria:
N2O3 ' NO + NO2
2 NO2 ' N2O4
If you do not keep on cooling the ampoule after sealing it,
the light blue solid substance will melt, first into a deep blue
liquid state which, because of the extremely high pressure,does not even disappear at room temperature (according to
the principle of Le Chatelier). Heating up the microampoule with a hairdryer enables you to demonstrate theconcentration of the brown gaseous state caused by theintensified production of NO2 from N2O4 within seconds.
In addition to the described phenomena, micro-ampoules enable you to demonstrate lots ofother temperature dependent chemical-physical processes („Instant Chemistry“!) [4].
Even in very large lecture halls, they can easily be visualized by means of modern video
cameras
4. A wine bottle opener as a source for N2O – the „barking dog“ without NO and CS2 [6]N2O (laughing gas) in high pressure steel ampoules is used to produce whipped cream.
Special wine bottle openers work with the same type of steel ampoules containing carbon
dioxide. Therefore those wine bottle openers
can also serve as source for N2O so that many
experiments involving N2O can be designed as„Instant Chemistry“ examples [5,6,7,8,9]
E.g.: Using the wine bottle opener it is possible
to fill a wide mouthed 1 litre glass bottle withlaughing gas within one minute. Instead of
poisonous CS2 normal rum (80% ethanol) is
evaporated at hot tap water temperatures so thatthe noise and the blue flash of the famous„barking dog“ can be performed with materialbought exclusively from the super-market. The
nice reaction may follow this reaction path:

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C2H5OH + 4 N2O → 4 N2 + 2 CO + 3H2O
2 CO + 2 N2O →2 N2 + 2 CO2_________________________________________________________________________________________________________________________________________C2H5OH + 6 N2O → 6 N2 + 2 CO2 + 3H2O
5. Microscale dry ice production and microscale liquefied laughing gas [10].
Two exciting and pretty examples of gases are well known in the kitchen: carbon dioxide andlaughing gas. Both laughing gas and carbon dioxide are simple substances in every day life.
Both laughing gas and carbon dioxide are stored in very similar looking steel cartridges forwhipped cream chargers and for soda siphon chargers. Both gases can be used in sufficientamounts for chemical education in a special wine bottle opener. [3,4,5]

Compared to carbon dioxide nitrous oxide is a gas with very similar physical properties (seetable 1). Many similar physical material data e.g. density, molar mass, solubility in water andcritical temperature can be demonstrated in a very simple way. Experimental stuff fromschools combined with special supermarket products is sufficient.
Table 1
Structure
Molecular mass
Litre mass
Melting point
Boiling point
Critical temperature
Critical pressure
Critical density

N2O
N=N=O
44,01 u1,997g/l-90,8°C-88,8°C
36,5°C72,6 bar
0,457g/l

CO2
O=C=O
44,01 u1,977g/l-57°C (5,2 bar)
-78,5° (sublimation)
31,06°C
73,83 bar
0,464 g/l

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The chemical properties and the physiological effects of nitrous oxide and carbon dioxidewith iso-electronic structures of its molecules are completely different.
Laughing gas is not only used to make whipped cream. Many students know that nitrous
oxide could be used for sniffing. Of course it is used in hospitals for anaesthesia, it is further
more well known as an very effective oxidizer in combustion engines. Using small amountsof laughing gas the properties as an oxidizing agent can be demonstrated in various simple
and timesaving ways [4-7].
On the other hand a soda siphon cartridge contains carbon dioxide which can be used as a fire
extinguishing gas. A special recipe to produce small amounts dry ice from one single soda
siphon charger gives us the chance to show the sublimation and the triple point in a small
syringe even for a big audience [6-10].
6. The basis of a safety match [11]Safety matches use a match head that is mainly KClO3, struck against the match box surface,which consists of non-toxic red phosphorus (about 50%). Placed outside the matchbox,
instead of in the match-head, the match can only be ignited through friction with the red
phosphorus panel. This is the basis for the safety match, which can be shown without any
laboratory equipment if only microscale amounts of the potentially dangerous chemicals are
involved. The reaction on a microscale level, stoichiometry, calculation, and safety goggles
prevent possible accidents.
Concerning the equation with
0,00010 mol (about 12,3 mg
finely powdered) KClO3 and
0,00012 mol (about 3,7 mg
dried phosphorous) a niceflash can be produced intheory. To be sure that the red
phosphorous
will
react
completely with the solidoxidizing agent and cannot
burn on the skin with theoxygen of the air, excess
KClO3 (about 40 mg) is
necessary and essential!
7) Pictures can say more than words
The described material for the low cost gas generation for many
microscale gas reactions can be stored in two or three plastic
video cassette boxes. Using this equipment more than hundred
different and context based reactions can be performed.
It should be noted that particular emphasis is laid on thedescribed test-tubes, syringes and ‘soft rubber’ stoppers. The
material used in these procedures is essential for being on thesafe side with successful results. If somebody uses other testtubes, disposable syringes and normal ‘red’ or black rubberbungs as available in most science education suppliers’
catalogues the described technique for a mobile low cost gas
generation without a fumehood will probably fail. The
following pictures should show the wide range of possibilities.

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The examples have been found to be particularly useful in demonstrating potentially very
dangerous reactions relatively safely on a very small scale but still with a spectacular result.
Chemical demonstrations and lab activities should be done as small as necessary, but not as
small as possible.
7.1. Inverse flames
Is oxygen able to burn? This question could arise during the inverse flame experiment which
was very famous in the
19th century (see figure
below). The potentially
dangerous experiment isdealing with pure oxygen
and pure hydrogen.
In a pure hydrogen
atmosphere pure oxygen
delivered from a small
tube seems to burn with anice flame, if the reaction
between the elements canbe started before a very
dangerous mixture can beformed. The reaction on anormal scale would be
dangerous. This may be
one of the reasons why
the inverse flame experiment disappeared out of thesourcebooks for chemistry teachers.

Using the described low cost material© with special test tubes, stoppers and syringes theinverse flame experiment can also be performed with pure chlorine delivered from a syringewith a small steel tube (needle with cut dip) on it. Chlorine seems to burn in pure hydrogen.

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7.2. Chemical vapour deposition (CVD) modelling experiment [12]Silane is generated by the reaction of magnesium silicide with 1 M HCl (aq) in the special
small test tube. Before this reaction can be initiated the air in the gas generator can be
replaced easily using a cooling spray (FHC). The generated silane can burn only at the end of
the glass tube as shown in the picture above. Through heating the glass tube the delivered gas
will be decomposed inside so that a thin film of silicon appears. The produced hydrogen canbe collected and detected.

Using a microflame the thin film silicon can be heated for demonstrating the semiconducting
properties of the layer (CVD). In addition the self ignition of silane is a nice experience.

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7.3. Self ignition of P2H4 [13]With a commercial rodenticide containing 28 %of Ca3P2 the self ignition of very poisonous PH3
contaminated with P2H4 can be shown similar
to the self ignition of silane. Small amounts ofchemicals in the small gas generator reduce thedanger and the time for the preparations.
7.4. Chlorine and bromine without a fumehood, photolytic reaction with pentane [14]12

7. 5. Sparks from a piezoelectric device for at least 20 various explosive mixtures [3, 15]

Warning: The short description of the experiments shown in the pictures and figures above isonly useful for this abstract. If somebody want to perform these potentially dangerous
experiments, the original literature [1-15] with detailed descriptions and helpful references fora safe troubleshooting is strongly recommended.

Literature:[1] V. Obendrauf, Low Cost Gas Generation for Small Scale Hands on Experiments, 16th ICCE, Budapest, 2000,
Book of abstracts[2] V. Obendrauf, Experimente mit Gasen im Minimaßstab. ChiuZ 1996, 30 (3) 118[3] V. Obendrauf, Die Low-Cost-Lachgas-Kanone. PdN-ChiS 1999, 48 (3), 35[4] V. Obendrauf, Gläserne Hochdruckbehälter im Mikromaßstab, PdN-Ch 2000, 49 (5) 4[5] V. Obendrauf, Lachgas auf Knopfdruck, Chem.Sch.(Salzbg.) 2001, 16 (2) 4[6] V. Obendrauf, Der „Bellende Hund“ m. Mitteln des Alltags, Chem.Sch.(Salzbg.) 2001, 16 (4) 11[7] V. Obendrauf, Sichtbarer Kohlenstoff aus unsichtbarem CO2, Chem.Sch. (Salzbg.) 2002, 17 (1) 13[8] V. Obendrauf, Von der Sahnekapsel zur Modellrakete, Chem.Sch. (Salzbg.) 2003, 18 (3) 12[9] V. Obendrauf, 40th IUPAC Conference, Beijing 2005, Keynote Lecture, Book of Abstracts 2005[10] V. Obendrauf, Trockeneis aus dem Supermarkt, Chem.Sch.(Salzbg.) 2005, 20 (4) 6[11] V. Obendrauf, Amorces, Partyknaller, Knallkorken, Pyrotechnisches Spielzeug, PdN-Ch 2003, 52 (5) 22[11] V. Obendrauf, Inverse Flammen, „Kann Sauerstoff brennen?“ Chem.Sch.(Salzbg.) 2005, 20 (1) 9[12] V. Obendrauf, Chemical Vapour Deposition, Microscale-Experimente mit Silan. PdN-ChiS 2005, 54 (1), 43[13] V. Obendrauf, Phosphan – Historische Experimente aktuell Chem.Sch.(Salzbg.) 2006, 21 (2), 11[14] V. Obendrauf, Small Scale Hands On zum rotbraunen Gift T+ (Brom). Chem.Sch.(Salzbg.) 2006, 21 (1) 11[15] V. Obendrauf, Feuerzeugbenzin im Arbeitstakt. Chem.Sch.(Salzbg.) 2000, 51 (3) 8

This article was reproduced from the Proceedings of the 19th International Conference on
Chemical Education, August 12-17, 2006, Seoul, Korea, pp. 10-21, with permission of theOrganizer.
Additional note by the author
It is an overview what is possible with my special gas generators. It is also a conclusion about
the advantages of microscale chemistry. The crucial point is to use the materials describedin particular for the equipment. Otherwise the colleagues could be disappointed. Different
syringes have different properties. If dangerous or poisonous gases are involved it isnecessary to follow the instructions in detail.