a

SCOTTISH SCHOOLS SCIENCE

EQUIPMENT RESEARCH

CENTRE

Bulletin No. 80. May, 1975.

Contents

Introduction — basic and workshop equipment list Page 1.

Biology Notes — disinfectant s 1.

In The Workshop — flask shaker 6.

Address List 10.

Bulletin Index, Nose 70 — 79 11.

4

Introduction

We have just sent to all our U.K. readers a copy of our basicand workshop equipment list. The list purports to cover the needsof any science laboratory whatever subjects may be taught there, anddeals with such items as burners, clamps and stands, test—tubes etc.In the workshop section vie have placed items, mainly expendable,which would normally be kept in the technician’s store and drawn fromas needed It includes things like glass tubing, mains cable,crocodile clips. Also in the workshop list we have included arepresentative list of what vie think is required by way of wood,plastic and metal, together with glues, paints etc. if the technicianis to be employed in the maintenance and repair of equipment, or in theconstruction of new designs of apparatus.

The list was priced in November, 197L, which is why it carriesthat date, and, to give some idea of the cost then of equipping alaboratory from scratch, the total cost of the items on the list,taking the lower of the two quoted prices where this is applicable,is as follows.

Basic equipraent £560.

Workshop equipment £830.

Workshop materials £250.

The figures are not exact but have been rounded up to the nearest £10•What they mean is that at the prices ruling at the time, it wouldhave cost an authority £1 ,1 00 plus £560 per laboratory designed for20 pupils to instal the basic equipment. To this must be added theequipment required for Integrated Science, or for the separatescience subjects.

Although the list has been sent to UK. readers only, we willsupply anyone from abroad who wishes a copy, on receipt of 15p (orthe equivalent in their own currency) with a clearly printed addressto which the list should be sent The same charge, which includespostage, applies to anyone in the U.K. who is not on our addresslist, or to anyone wishing additional copies.

Biology Notes

In Bulletins 71 and 7L1. there was seine discussion of the problemof plastic Petri—dish disposal. If our information is correct,some teachers are solving the problem in a potentially hazardousmariner It would seem that they may be soaking used dishes in Lysol,washing them in soapy water, and then re—using them for non—microbiological iiork — as storage containers, crystallising dishes etc.It cannot be emphasised too strongly that treatment with Lysol doesnot sterilise the dishes ysol, in common with other phenolicsolutions and derivatives, is not sporiciclal and any dishes washedin it, may well remain contaminated. Used dishes should be disposed of

—2—

by the recommended methods. There is, as far as we are aware, noreliable way to ensure that dishes are completely sterilised exceptby autoclaving or some other form of heat treatment, after which theyare in no state to be re—used, If teachers are upset by the wasteof material and environmental contamination inseparable from the useof plastic dishes, they can always join with a number of theircolleagues who have returned to using nom—disposable, but highlybreakable glass Petri—dishes,

The misuse of Lysol has lead us to consider the general problemof disinfection, A large number of different chemicals can be usedto kill or control micro—organisms. Their action can be fungicidal,bactericidal — killing bacteria but not necessarily their spores,virucidal, sporicidal, or germicidal. The last is strictly, amisnomer, A germicide kills almost all micro—organisms, there beingno known liquid germicide which is completely effective against allorganisms. Some chemicals act merely as bacteriostats, preventingthe growth of bacteria without necessarily killing them. For schoolusage the choice of disinfectant has to be made after consideringseveral factors. The most important and most obvious of these isthat the chemical(s) used should be known to be effective againstthe organisms involved, under the conditions likely to be encountered.For example, it serves little purpose to use a non—sporicidalcompound which is inactivated by the presence of organic matter whencleaning cages. Another important consideration is that thesubstance used must not be harmful to the user or to livestock.Toxic preparations and, as far as this is possible, those which actas irritants, should not be used in schools. Lastly there is theissue of cost. This involves two factors, the price of the liquiddisinfectant itself and the normal working concentration, which willdetermine the actual cost per unit volume of disinfectant solutionas used in the laboratory. When making up dilutions from concentrated disinfectants it is advisable to use distilled or freshlyboiled water, so lessening the risk of any contamination withresistant organisms. Bottles used to store the diluted solutionsshould never be fitted with corks, as these can inactivate manydisinfectants,

The table below summarises some of the relevant information onthose disinfectants encountered in laboratories,

Action. Recommended Use Dilution.

B — bactericidal D — dirty equipment, cages etc.

Bs — bacteriostatic G general disinfection of

F — fungicidal‘clean’ glassware, equipment etc.

V — virucidalI — instruments

Tb — effective against— sicin disiifection

tubercle bacilli

— S ri dal C — swabbing of ‘clean’0 Ci surfaces, hard floors etc.

hd — at high dilution

Dis

infe

cta

nt

Appro

x.

cost

per

Acti

on

Rec

om

men

ded

uses,

No

tes

litr

eof

work

ing

toxic

ity.

so

luti

on

and.

work

ing

concentr

ati

on

(v:v

aqueous

solu

tio

n).

?och

lorit

es

‘On

loro

s’S

olu

tio

ns

G,

CG

ood

for

genera

lm

icro

—bio

logic

al

co

nta

inin

gat

use.

Irrit

an

t,corr

osiv

epr

op—

‘Lil

ton’

Iple

ast

20

0B

,S

p‘°

Serti

es

mea

nuse

isrestr

icte

dto

p.p

.in,

avail

—b

d.i

sin

fecti

ng

cle

an

gla

ssw

are

,M

aws

‘Sim

pla

’able

ch

lori

ne

mer

nran

es

sp

illa

ges

and.

pre

—tr

eatm

ent

of

sho

uld

be

used.

orrosiv

eo

mate

rials

Pri

or

todis

posal.

meta

l,sh

ou

’dH

eavy

conta

min

ati

on

wit

ho

rgan

icno

be

use

don

matt

er

mea

ns

usin

gsolu

tions

wit

hI

to20

avail

able

ch

lori

ne.

Ble

ach

ing

acti

on

pre

clu

des

use

on

Vic

arpro

tecti

ve

glo

ves.

clo

thin

g.

?lc

ohols

Eth

anol

.7

5i

5k,

I(m

oo.

Use

usuall

yrestr

icte

dto

mic

ro—

,—

—lo

ops).

bio

log

y—

as

aero

so

ls,

swab

bin

g,

,,

,

ce

ing

.Loo

psS

pr1S

25p

1:lto

B,

Tb

Som

eris

of

etc

.U

sed

todis

infe

ct

skin

(Indastr

ial

I2

.5.1

toxic

ity.

befo

reta

kin

gb

ioo

sam

ple

s.sp

irit

s)

Poenti

al

fir

eA

cti

vit

yre

du

ced

inp

resen

ce

of

zar

org

anic

matt

er.

No

tsp

ori

cid

al.

Phenoii

cs

‘Lv

so]i

to1

10

0to

B,

F,

To

xic

,ir

rit

ant.

No

longer

reco

mm

ended

for

school

(cre

zo]/

soap

21

•2

0B

s(h

d),

Pote

nti

all

yvery

labora

tory

use.

Com

pati

ble

wit

hm

ixtu

re)

p•

V1hazard

ous

inth

eso

ap

but

not

fats

or

oil

s.

Not

undil

ute

dsta

te.

sp

ori

cid

al.

1.

Dis

infe

cta

nt

Ap

pro

x.

cost

per

Acti

on

Reom

mended

uses,

Note

sli

tre

of

work

ing

tox

icit

y.

so

luti

on

an

dw

ork

ing

co

ncen

trati

on

(v:v

aqueous

so

luti

on

).-

Solu

tions

wit

hM

aybe

use

don

cages

but

pla

sti

cs

25

—150

p,p

.m.

and

rub

ber

can

ab

sorb

much

of

the

avail

able

G,

I,

C,

avail

able

iodin

e.

Corr

osiv

eto

iodin

e;

up

toB

,S

p,

Rela

tively

non—

meta

lat

hi&

co

ncentr

ati

on

s.

Colo

ur

indic

ate

sle

vel

of

‘Wes

cod

yn

e’l—

2p

10

00

p.p

.m.

inF

,T

b,

irrit

an

tir

use

dare

as

heav

ily

V.

acti

vit

y.

Not

gre

atl

yaff

ecte

dco

rrectl

y.

conta

min

ate

db

ych

ang

eo

fpH

or

org

anic

wit

ho

rgan

icm

att

er.

matt

er,

guate

rnary

_A

mm

oniu

mC

opounds

(QA

Cs)

‘Task

’D

o1

10

0D

,S

k,

G,

C.

Acti

vit

yre

duced

by

org

anic

matt

er

9,

.A

cti

ve

film

‘eft

on

treate

d‘s

av

ion

’8k,

G,

C;

Vir

tuall

ysurf

ace,

Com

pati

ble

wit

hm

eth

ax-a

lli

quid

0W

flto

B,

non—

toxic

at

and.

alk

ali

s,

not

wit

hanio

nic

sor

anti

septi

c1

20

0or

Bshd,

wo

rkin

gle

ss

dep

en

d-

Tb

hd

,concentr

ati

on,

soap

s,

Oft

en

mo

reacti

ve

again

st

ig

ram

+v

ety

pes

but

pre

para

tions

‘Savio

n’

ing

on

cir

cm

—S

1in

sensit

iz—

wit

h‘H

i.bit

an

e’

are

more

acti

ve

hospit

al

sta

nces

an

dati

on

and.

co

ncen

trate

indiv

idual

irrit

ati

on

ag

ain

st

gra

m—

yeorg

an

ism

s.N

ot

spo

ricid

al,

‘Ase

pto

po

l’pro

duct,

report

ed

but

no

tco

mm

on

,

holytes*

Goo

dall

—ro

und

dis

infe

cta

nt.

‘Teg

oM

HG

’1

pD

,G

,I,

Sk,

C•

Usefu

lfo

rcag

es

etc

.C

ompa

t—B

,B

a,

Vir

tuall

yib

lew

ith

man

ysurf

ace

acti

ve

‘Gri

ffin

AS

AB

’3-

1100

F,

Sp

,non—

toxic

and.

agents

,in

clu

din

gQ

AC

s,b

ut

not

Tb.

no

n—

irri

tan

t,w

ith

soap.

Leaves

acti

ve

‘Harr

isB

AS

’3p

su

rface

film

;d

eo

do

risin

g;

.acti

vit

ynot

reduced

by

org

an

ic

[_

__

__

__

__

__

__

__

__

_—

4:-

F.

*pio

1ic

s.

‘Ly

sol’

isth

ephenoli

cpre

para

tion

most

com

mon

lyen

co

un

tere

din

school

labora

tori

es.

Wh

ilet

we

ad

vis

eag

ain

st

the

use

of

Lyso

l,so

me

pre

oara

tions

co

nta

inO

fli

the

hiier

phenoli

cs

an

dare

less

irrit

ati

ng

and

tox

icT

he

main

advanta

ge

of

such

dis

infe

cta

nts

isth

eir

rela

tive

cheapre

es

an

dth

ere

ten

tio

no

facti

vit

yin

the

pre

sen

ce

of

org

an

icm

att

er.

We

would

not

rule

out

their

use

inso

me

sit

uati

on

s,

e.g

.fl

oors

,fo

otp

ath

san

d.oth

er

larg

edir

tyare

as,

**

Am

r.o

lyte

s.

Th

ese

are

&iC

Oacti

ve

ag

ain

st

som

ev

iru

ses,

part

icu

larl

yth

ela

rge:.

po

xty

pes,

e.g

.anim

al

pox

vir

uses

There

isso

me

co

nfs

ion

betw

een

lab

ora

tory

ani.

fie

ldtr

ial

result

sas

toth

eeff

icie

ncy

of

acti

on

ag

ain

stoth

er

vir

uses

and

there

fore

we

hav

en

ot

descri

bed

these

com

pou

nd

sas

bein

gvir

cid

al

alt

ho

ug

hth

ey

do

sho

wco

nsid

era

ble

anti

—vir

al

acti

vit

y.

+Jd

ed

fs,

meth

ara

lsciu

tio

no

nfil

ter

paper

can

he

use

dto

pro

vid

em

eth

ans.

].vapour

tok

ill

icro

—o

rgan

isis

inP

:tri

-dis

hes

by

treatm

en

tovern

ight

befo

rein

spscti

sn

of

cult

ure

sby

pupil

s.

Ho

wev

ersu

ch

inspecti

on

isra

rely

necessary

and

ifatt

em

pte

dth

epro

cedure

reco

mm

ended

by

M,I

,S,A

0C,

should

he

foll

cw

ed

(School

Scie

nce

Revie

w,

No

,1

95

,(M

I.S

.A,C

.M

icro

—b

iolo

gy

inS

chools

Ad

vis

ory

Co

mm

itte

e;

nam

esand

addre

sses

of

.oca]

ad

vis

ers

inS

cotl

and

are

giv

en

inth

eJourn

al

of

Bio

log

ical

Educati

on,,

1,

Febru

ary

,1

97

5.)

,

I

Dis

infe

cta

nt

Ap

pro

x.

cost

per

Acti

on

Rec

om

men

ded

uses,

No

tes

litr

eo

fw

ork

ing

toxic

ity,

so

luti

on

an

dw

ork

ing

concentr

ati

on

(v:v

aq

,ueo

uss

olu

tio

n),

Ch

ioro

xy

len

ols

‘Dett

ol’

5p

8k,

I;1:

20

Bk

,G

,r

‘G

ood

for

use

inre

lati

vely

,‘.

Jo

‘cle

an

’are

as,

Acti

vit

yB

ootB

’Fam

uly

2p

G;

1L

0B

,L

ittl

eto

xic

ity,

reduced

inpre

sence

of

Anti

septi

c’

Can

be

irrit

ant

‘IZ

S.i

whe

nu

nd

ilu

ted,

org

anic

matt

er,

Anti

septi

c’

1C

;1

150

Meth

anal

Usu

all

y1

50

B,

Be,

Hig

hly

irrit

ant

Not

reco

mm

ended

.fo

rsc

ho

ol

use

(Form

ald

ehyde)

Ip

toI

:2

0F

,S

p,

and

toxic

,V

apou

rbecause

of

toxic

ity

and

V.

may

com

bin

ew

ith

irrit

an

tp

rop

ert

ies,

hydro

chlo

ric

acid

vapour

tofo

rma

carc

inogen,

-—

—6—

Local wharmacists will usually be able to supply Dettol, Boots FamilyAntiseptic, Izal ntiseptic, Chioros, Milton, and Maws Simpla. Othersuppliers are; Tego MHr — Houh, Hoscsaon nJ Co.; G-riffin A0’B —

Lifn.n anI Gcorp-e, Harris BaD — Philip ILrrlD Biological, Task andAseptopol — British Hydrological Corsorstion; Savlon products — 1.0.1.Wescodyne — Ciba—Geigy.

In The Workshop

The origin of this design caine from the Berwickohire High school,Duns. The use of an oscillating shaft in a flask shaker is not new;it features for example in the Griffin and Gcor version. Wherewe have departed from custom is in the method of linking the shaftto the drive mechanism. The usual connecting link system couplesthe shaft to the drive permanently. We have noticed that on soniccommercial versions this tends to move the liquid bodily, whichproduces relative motion and presumably solution between the liquidand any heavy particles lying on the bottom of the flask, but doeslittle for any that are in suspension. Vie decided therefore thatwe would use the drive only to displace the shaft from itsgravitationally stable position, and use gravity to effect the returnof the shaft for the next strokes This produces a jerky motionwhich really shakes up the material in the flask; in foot we havefound that if the stopper is not secure it can be snL’kun loose andthe liquid spilt. At the same time we built in a q.uick method ofadjusting the degree of shaking by varying the amount of displacementof the shaft• The principles will be seen in Fig. 1

At one end of the shaft carrying the flasks is keyed a long pin,

like a knitting needle, which projects downwards. iear base levelthis is in the path of two projecting pins sited on a disc which isturned at a speed of about one revolution per second by a motor.Each pin in turn impinges on the needle and moves it to one side.

lIon the rotation of the disc carries the pin beyond the end of theneedle, the weight of the flasks causes shaft and needle to drop backuntil the needle strikes the second pin. This sudden arrestinent oftIi return produces the jerky motion, and turbulence of the flaskcontents. The position of the needle on the shaft relative to the‘rest’ position of the flasks may be altered, moving it to one orother side of the vertical, and this produces more or less vigorousshaking.

The oscillating shaft is a piece of oak or other hardwood,300 x 25 x 25 mm On each of the sides are screwed three Terryclips to hold the flasks, six of size Li. and six size 3 in all.The size L clip will take a 250 ml conical flask, while size 3 fitsthe necks of 250 or 350 ml round flaaks• The clips are not scrusuddirectly to the shaft; instead, small pieces of wood, used solelyas spacers so that flasks on opposite sides of the shaft will not bein contact are placed imdei’ each clip. Pieces of hardboard wereused under the size Li. clips, arid of 5 mum thick plywood under thesize .3 clips. Also, to avoid we:iiening the shaft by having four

—7—

screws entering at the same cross—section plane, the placings of theclips on the four sides of the shaft are offset by a small amountrelative to each other. Clips on the same side of the shaft areabout 10 cm apart. For balance the same size of clip and flaskmust be put on opooite sides of the shaft. The capacity of theshaker is therefore six flasks of the same sizes If only one flaskrequires shaking, it must be balanced by a similar water—filledflask on the opposite side•

At each end of the shaft a 10 mm dia. hole is drilled 25 mmdeep. Into these are fitted two lengths of 10 mm dia, mild steelrod, so that they project 25 mm at one end, and. mm at the other.In our case these were secured with Araldite. These rods supportthe shaft on two L brackets, made from 6 x 25 mm mild steel bar, sothat it is about 18 cm above the baseboard. Two nylon bushes areused between the rod and brackets. Details of this part of theconstruction are shown in Fig. 2.

The drive mechanism fits on to the longer of the two rods, andis shown in Fig. 3. It is made from mild steel rod, 25 mm dia.,turned down on the lathe to 20 mm dia. at one end. The driveneedle, which could well be a steel imitting needle, in our case wasa length of 3mm mild steel rod brazed into the bush to a depth of 5 mm,The length of the needle is about 15 cm; it should be made so thatthe end is level with the drive shaft of the worm gear. One or moreAllen type grub screws are used to lock the bush onto the shaft ofthe shaker, The end 20 mm of the needle is covered with a lengthof polythene or polypropylene tubing, largely to reduce noise fromthe drive pins striking the needle. Thus when the grub screws areloosened, the position of the needle on the shaft may be adjusted sothat the needle is in contact with the drive pins for only a smallfraction of the rotation, producing gentle shaking, or over almostthe whole of the rotation cycle, giving more vigorous shaking.Again, when changing from one size of flask to the other, the screwsare loosened and the shaft turned through 9Q0

The motor drive is shown in Fig. L4. Two 25 mm long Li- BA boltsare fixed LO mm apart and diametrically opposite on a Li-5 mm brassdisc which has been silver soldered to a brass bush suitable forfitting the motor shaft, The bolts are covered with nylon tube,again to reduce noise and for good wearing. These sleeves are aloose fit on the bolts so that they rotate when in contact with theneedle, Any motor which will provide the necessary torque and. run.continuously will be suitable. A final speed of one revolutionper second indicates that one with a worm gear may be best. Amongstour surplus material we have a motor of this type, in sufficientnumbers to be able to offer it to any who wish to construct the flaskshaker, Unfortunately it is designed for intermittent use at 115 Vand requires additional components to be bought to adapt it for 2Li.0 Vcontinuous running. Despite this we think that it is still possibleto construct a cheap and effective flask shaker using the motor.The remainder of this article will therefore deal solely with theadaptations necessary to use our motor with the shaker,

The package as supplied — cost 50p plus postage — will consistof !otor, Li—terminal connecting block, starting capacitor, and wormgearing. The following additional components will be required.

—8—

Auto_transIormer, K. R, Whiston 5107 £1.6221j.0/115 V

Toggle switch R,3, Domponents 31—563 26pFuse holier )t12—021 2p500 mA fuse .1L12—138 ipPower resistor, 15Li—)38 2lp

0.7 A

An alternative auto—transformer is the R,S. Components 207—116 at£2.70. The electrical circuit of the mtor is shown below,

— —- I

:Connections to the right of the lotted line will normally have

been made on the ecuipmcnt as supplied by us, although in caine casesthe earth connection to the motor may be riiseing, There are anumber of screw holes in the motor case to which this connection maybe made• The colour—coded leads between the motor and the connectorblock are B/0 = black/orange; Bl = blue; B = black. The auto—transformer leads have standard coding on both primary and secondary,i.e. brown = live; blue = neutral; green/yellow = earth. The powerresistor was included in the motor input to reduce energy dissipationso that the motor, even when boxed in, would run continuously withoutoverheating, It has the same beneficial effect on the transformer,and it does not affect the performance of the motor. Using theresistor, the p.d, applied to the motor ic about 100 V and thecurrent 0.5 A,

The motor shaft is threaded for a worm drive • The worm gearinsupplied consists of a worm wheel on a shaft and two other connectedgear wheels, all on a U—bracket. The gearwheels are not needed and.should be removed. One is fixed to its shaft with a circlip, the.other is secured by a pin through the wormshaft which must be pulledor hammered out. A spacer, also pinned on the worm shaft shouldalso be removed. The worm wheel is fixed to the shaft with anAllen grub screw; this should be loosened and the vtheel moved sothat it is at the end of the shaft. This allows the shaft to bepushed further into the U—bracket so that its far end projects I’arenough beyond the bracket for the attachment of the brass disc ofFig. J4., The worm shaft is 6,L1. mm (* in) diameter, and thedimensions given in Fig, L should fit it, It will be necessary todrill two holes in the base of’ the bracket to allow it to be screweto the baseboard. Fig. 5 shows the find appearance cf the wormdrive,

Our base was a pieee eJ 20 mm biocdioard measuring 60 x 25 cm,This is large enough to contain the shaker, the motor, and itsassociated circuitry, We think that the motor is powerful enough todrive a total of’ 8 250 ml flasks, I’uUI’ to a side, and if this wereIoiie the btseboard and. usciilating shafU eould ruu1L’u to be lenjt’—

w1 - ‘e mae a eovr t’or a1 1 i ‘iv ng i1iacian xe pt t1nLsc .iitl (iLiVe T]-, U31fl r.’ mild ti-_l. This

• bs4

0 —9—

serves the double purpose of insulating pupils from contact withhigh voltages, and protecting the equipment from spillages from theflasks. The cover carries the switch and fuseholder at one side,but all other components are mounted on the baseboard. Theremaining sides of the cover have gauze—covered vantilation holesand it was also painted matt black to help heat dissipation. Infact none of the components runs so hot as to be uncomfortable to thetouch. After all components have been mounted the baseboard andL—brackets should be given a protecting coat of varnish. To dateour shaker has run continuously for six weeks with a load of six250 ml flasks each containing approximately 150 ml water.

\ S \\‘\

[S

former shaft wormnot required I

Lt

200

1.

Fig. 2.

ft\ f\

needle

Fig.

Figures not to scales

_______

Dimensions in mm.

/

VFig. 5.

rHil

7 77 757 V(D

________

-

‘—5---’-

—‘

L1

h.p

— 10—

S.C.S.E.R.C., 103 Broughton Street, Edinburgh, EHI 3RZ.Tel O51 556 218L.

British Hydrological Corporation, Colloidal Works, Deer Park Road,London, SWI9 3UQ.

Ciba—Geigy (UK) Ltd., Agrochemical Division, Whittlesford,Cambridge, CB2 LQT.

Griffin and George Ltd., Braeview Place, Nerston, East Kilbride,Glasgow, G7L 3XJ.

Philip Harris Biological Ltd., OicLrnixon, Weston—super—mare, Avon.

Hough, Hoseason and Co. Ltd., Levenshulme, Manchester, M19 3PT.

I.C.I. Ltd., Pharmaceuticals Division, Alderley House, AlderleyPark, Macclesfield, Cheshire.

R.S. Components Ltd., P.O0 Box L27, 13 — 17 Epworth Street,London EC2P 2HA.

K. R. Whiston, New Mills, Stockport 12 4PT.

Bulletin Index, Nos. 70

Accidents in laboratories 70,5; 79,5.Ammonia, combustion in air 72,10.Ammonia, decomposition by sparking 70,l-j-.Ash content determination 71 ,7.

Blowpipes for natural gasBridge rectification model

Calculators, test reportCalculators, test summaryClinistix test stripsCollapsed can experiment, using ring—pull cans

Didacta exhibitionDiluter for disposal of liquid wastesDispenser for constant volume of liquidsDissolved oxygen measurement

Electrical components testerElectronic calculators, test reportElectronic calculators, test summaryElectrostatic field demonstrationEquilibrium constant of lead sulphate/sodium iodide

Flameproof cabinets tests 75,2; 78,6.

Gas lighters, natural and town gasGas lighters, test summaryGlass tubing, how to abrade with wire gauze

Hazardous chemicals, disposal ofHeats of neutralisatjon

Integrated Science equipment listIntercostal muscle model

Lever apparatus designLung contamination, smoking doll desi

—11 —

79.

71 ,3.77,6.

70,7.70,9.71 ,6.78,6.

73,2.73,7.73,9;78,3.

71 ,1.70,7.70,9.71 ,278,11.

7L., 9.

7L1. , 77L1,1 1.77,11.

70,171 ,5.

7L,177,10.

75,11.73,1 0.

76,3; 77,2.76,9.76,5.7L, 6.72,11.79,179,6.79,8.

Melting point apparatusMethane substitution molecule modelMicro—biology hazardsMicro—biology kit, GriffinMicroscopes, test summaryMillon’s reagent, haza.tlds and alternativesMolecular weight of gases determinationM alt i—vibrator design, using integrated circuit

pH electrode simulator designpH meter modified for demonstrationPaper chromatographyPeak and r.m.s. values of alternating currentPelican crossing sequence modelPen recorder as a timing devicePhoto-micrographyPrecipitate washing, automatic

Resistance wire former 75,10.

SYS alternating current experimental guide,correction

Silver recovery methodSodium street lamps as spectrum sourceSoldering iron design for battery operationSciuare wave oscillator using integrated circuitStethograph and tambour designSurplus ecuipment

Test summary, electronic calculatorsTest summary, gas lightersTest summary, microscopesThermo—chromic liquid recipeThermo—electric effect apparatus designThermometer life—saverTicker tape dispenser design

72,1.73,7.79,7.72,8.79,8.75,14.72,8; 714,2; 77,3.

70,9.714,11.72,11.70,5.76,8; 77,6.75,10.79,10.

— 12 —

78,1 0.75,8.76,14.77,8.72 , 2.70,2.73,14.76,14.

Velocity of sound in a metal rod 76,5w