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DRAFT TANZANIA STANDARD  
 
 
 
 
 
 
 
 
 
TBS/CDC -7 (5160 ) P3 Code of safety for sodium hydroxide (caustic 
soda)  (Rev TZS 379:198 9) 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 
 TBS/CDC -7 (5160 ) P3 
 
©TBS 2017 – All rights reserved      Second edition 2017  
 
 
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Foreword  
 
This Draft Tanzania Standard is being developed by the Industrial and Laboratory 
Chemicals Technical Committee under supervision of the Chemical s Division 
Standards Committee and it is in accordance with the procedures of the Bureau.  
This second edition after b eing finalized will cancel and thus replace the first edition 
TZS 389 :1989 Code of safety for sodium hydroxide (caustic soda) . 
This draft Tanzania Standard has been prepared with assistance drawn from:  
IS 4264:2013 Code of safety for caustic soda published by Indian Bureau of 
Standards.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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DRAFT TANZANIA STANDARD                          TBS/CDC -7 (5160 ) P3 
 
Code of safety for sodium hydroxide (caustic soda)  
 
1 Scope  
This Draft Tanzania Standard specifies a code of safety concerning hazards relating 
to sodium hydroxide. It describes the properties and essential informa tion for the 
safe handling and use of sodium hydroxide.  
2 Properties of sodium hydroxide   
2.1 Physical properties – Important physical properties are  
i. Physical state – solid 
ii. Colour – white or light grey  
iii. Melting point – 583K to 593  K 
iv. Hygroscopic ity – hygroscopic and deliquescent  
v. Solubility – 4.2 g/100 ml at 273K, 347 g/100 ml at 373  K  
vi. Boiling point – 1663  K 
vii. Specific gravity – 2.130  
 
2.2 Chemical propert ies  
2.2.1 Sodium hydroxide corrodes clothing and few metals such as aluminium, tin, 
zinc and alloys containing these metals, slowly corrode  iron, copper and Monel 
metal.  
2.2.2  Considerable heat generated on adding water to solid sodium hydroxide or its 
strong solutions may cause boiling and spattering of hot solution.  
3 Hazards  associated with sodium hydroxide  
3.1Health hazards  
Sodium hydroxide is dangerous when carelessly han dled. Its solid or solution form 
has marked corrosive action on all tissues of body. Signs and symptoms or irritation 
do not immediately become evident after contact with caustic soda, as a result, the 
user may suffer injury before she/he realises that the chemicals is in contact with 
her/his body.  
3.2 Acute toxicity  TBS/CDC -7 (5160 ) P3 
 
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 3.2.1 Lethal effects  – Sodium hydroxide is dangerous to live tissue. Contact with it 
causes burns, frequently deep ulceration and ultimate scarring. Severe burns result 
not only from the solid alkali but also from solutions of this compound. Even dilute 
solutions on prolonged contact exert a destructive effect on tissues. Sodium 
hydroxide is a strong primary irritant. Multiple small burns may result from exposure 
to dust or m ist of the material. Contact with eyes either of solid sodium hydroxide or 
its solutions may rapidly cause severe damage to the delicate eye tissues. Molten 
sodium hydroxide causes severe injury due to its high temperature (above 593K) 
and corrosive nature  which  results in damag ing mucous membranes of deeper 
tissues. As a result, perforation may follow or subsequent extensive corrective 
surgery may be required. Inhalation of the dust or concentrated mist may cause 
damage to upper respiratory tract and even to the lung tissue. The effects of irritation 
may vary from mild irritation of nasal membranes to severe pneumonitis depending 
on the severity of the exposure.  
3.2.2  Systemic effects - No general or systemic effects are noted except those 
resulting from shock or those secondary to tissue damage.  
3.3Chronic toxicity  
3.3.1  Local effects - Repeated contact with dilute solutions may cause superficial 
destruction of skin in multiple areas a nd primarily irritant dermatitis may result. 
Repeated inhalation may similarly cause varying degrees of irritation to the tissues of 
the respiratory passage.  
3.3.2  Systemic effects - There are none except those secondary to tissue damage.  
4. Handling,  storage and transportation  
4.1 Handling  
In handling sodium hydroxide solution , care should be taken to avoid solidification in 
the pipe lines and equipment. The strength of the solution may be easily determined 
from its density. All equipment should be kep t clean by washing of the accumulation 
of solidified sodium hydroxide and sodium carbonate that forms around small 
leakages. When disconnecting equipment or pipe lines, make sure that they are 
empty of sodium hydroxide and they are washed. At such times, a  hose with running 
water should always be available. Glandless pumps should preferably be used; 
otherwise packing glands of pumps should be shielded in order to pre vent spraying 
of sodium hydroxide solution. When spill age of solid or flakes has occurred , it should 
be swept carefully with a broom and the area hosed down. In case of spillage of 
solution, the flow should be washed with water from a hose rather than swept.  
4.1.1  Molten caustic soda has a temperature range of 593  K to 673  K. Extreme care 
shou ld be taken to avoid spurting of molten sodium hydroxide in the sodium 
hydroxide yard. The yard should be always kept clean. Any overflow or spillage of TBS/CDC -7 (5160 ) P3 
 
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 molten sodium hydroxide should be allowed to solidify and then immediately washed 
away; otherwise a dan gerous slippery surface will be left on the floor. Handling filled 
drums of molten sodium hydroxide is a dangerous practice which should not be 
followed unless the operator is well guarded. If hot sodium hydroxide is to be run into 
a container, extreme cau tion should be exercised to prevent splashing . 
4.1.2  Accidents frequently occur while taking samples of molten sodium hydroxide. A 
long-handled  nickel or steel ladle of small capacity should be used to scoop out the 
sample. It is not advisable to take samp les of flowing molten sodium hydroxide as 
there is always danger of spurting. Goggles, gloves, gum boots, aprons and safety 
helmets should be invariably worn whenever handling molten sodium hydroxide. The 
supervisory staff should constantly bear in mind th at all safety equipment should be 
properly  and constantly used. The most common hazard is to the eye and should 
always be protected by suitable goggles. Use of transparent face shield is 
recommended in addition to safety goggles.  
4.1.3 Solid sodium hydrox ide should be ground and flaked in a separate  well 
ventilated room remote from other work rooms. Each man in the grinding room 
should be provided with adequate type of pe rsonal protective equipment.  
4.1.4 Equipment for handling  
4.1.4.1  Pots containing boiling sodium hydroxide should be provided with exhau st 
hood to carry off the mists and sprays.  
4.1.4.2 Evaporators and similar vessels used in handling liquid caustic soda u nder 
pressure should be tested periodically with cold water acc ording to the standards laid 
down in the relevant pressure vessel code.  
4.1.4.3 Tanks should be provided with overflow arrangements in such a way that the 
liquid is conveye d to a safe place without causing harm to workers nearby.  
4.1.4.4 Stuffing boxes a re sources of leaks . With mode rn materials of construction 
and gland packing or seals, this leakage may be well controlled.  
4.1.4.5 To prevent leaks, pipe lines should be of seamless type and have welded 
flange joints. Dependi ng on temperature and pressure, the gaskets may be of soft 
rubber or compressed asbestos.  
4.1.4.6 Pipelines exposed to low temperatures should be arranged so that they can 
be heated to prevent crystallization of the solution.  
4.1.4.7 All equipment used for manufacture, handling, storage or use of c austic soda 
should be regularly inspected and maintained in good condition.  
4.1.4.8 During maintenance work when pipes are to be disconnected, workers 
should operate from above. Before breaking the point,  they sho uld ensure that there 
is no pressure inside and that the line has been thoroughly drained. Thoroughly TBS/CDC -7 (5160 ) P3 
 
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 rinsed with water; flanges s hould always be opened from the far end. The valve 
which controls the line should be closed and locked and a 'MAN AT WORK' sign 
should be hung on it until the repairs are complete.  
4.1.5 Dissolving sodium hydroxide  
4.1.5.1 Strip the drum and immerse the cake of solid sodium hydroxide in the  
dissolving tank of water.  
4.1.5.2 Perforate the drum suitably and suspend it above the dissolving tank and 
pump a stream of water into the drum allowing the solution to flow into the dissolving 
tank.  
4.1.5.3 To avoid iron contamination, peel off the steel drum from the solid cake of 
sodium hydroxide before dissolving. In bulk addition,  rapid generation of heat is 
obtained and there is like lihood of local boiling and spurting of the solution. Dissolve 
flakes b y addition to a well -agitated tank of water. Accidents frequently occur during 
the handling of sodium hydroxide for making solutions and it is imperative that all 
safety equipment is properly used in this dissolving department.  
4.2 Storage  
4.2.1 Drum con tainers should be stored in dry locations to prevent rusting. They 
should be periodically inspected and spills, etc, attended to. Rusted containers 
become weak and they should be handled with extra care.  
4.2.2 For station ary storage, mild steel tank or any other properly designed tank with 
alkali resistant lining should be used. They should be provided with manholes of at 
least 60 cm diameter protected with grills and cover. Top of the tank should be 
vented to atmosphere.  
4.2.3 All tanks should be capable of being completely isolated from other tanks and 
processes by suitable valves. Where possible small portions of pipe lines should be 
removed or blanks should be inserted for additional safety. The tanks should be 
capable of being drained off completely.  
4.2.4 Before repairs or cleaning, tanks should be completely drained and thoroughly 
washed.  
4.2.5 Person required to enter a tank should first make sure that the tank is empty, 
and has been washed free of alkali and certi fied so by a competent authorized 
inspector or inspecting authority. They should wear adequate personal protective 
equipment including a safety belt securely attached to a rope the free end of which is 
held by person standing outside the confined space. Su pply of fresh breathable air to 
persons inside the tank should be ensured by proper means.  
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 4.3 Transportation  
General precautions ; 
4.3.1  Close the lid or cover of the container so that i t is airtight in order to avoid 
moisture absorption during transpor tation.  
4.3.2  For transportation in drums, use box -cars, but if open -topped vehicle is used, 
cover the drums with sheets.  
4.3.3 Since crystals are precipitated from liquid ca ustic soda when the temperature 
lowers, do not expose it to low temperatures for a  long period of time.  
4.3.4  The freezing point of standard commercial liquid caustic soda is 5 -12°C  
4.3.5  When solid caustic soda is being handled dire ctly, or liquid caustic soda is 
being handled, be sure to wear protective gogg les and rubber gloves, and wear 
rubber boots or rubber clothing as required.  
4.3.6  Dispose of items contaminated by ambient caust ic soda mist, or that have 
been soaked in liquid caustic soda, after treatment to make them harmless.  
4.3.7  Since caustic soda generates heat when it is d iluted by water or neutralized by 
an acid, and may form a mist, make sure the eyes or skin are not exposed to the 
mist.  
5 Tankers  
Precautions with tankers - The following points are important to be noted:  
a) tankers, unless they are specially meant for stor age and transport of 
caustic soda solution, should be thoroughly cleaned of all extraneous 
matter before use.  
b) during loading and unloading, the tanker should be braked and isolated 
against any movement.  
c) while loading,  and unloading, spurting should be avoided and as an 
additional precaution anti - splash screens should be used.  
d) work on tankers should be supervised by foreman and only workers using 
approved type of personal protective equipment should be allowed to 
work .  
e) compressed air should not be used for loading or unloading the tank 
wagons but pumps or  
gravity method should be used.  
f) all valves should be closed before disconnection.  
water should be freely available and used in case of spillage.  
g) when empty, all op enings and valves should be properly closed and the 
tanker returned promptly.  
h) safety instructions should be stenciled on both sides of the tanker.  
 
 
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 6 Packing and labelling  
6.1 The containers of sodium hydroxide should be labelled  with a pictorial marking of 
"CORROSIVE," in accordance to relevant Tanzania standard which contain the 
following text:  
'SODIUM HYDROXIDE (CAUSTIC SODA),  
Danger: Do not get it in the eyes, on skin or on clothing. Do not take internally. 
In case of contact, flush with water copiously; in case of eyes flush with water 
for 15 minutes and see the doctor. Use goggles, face shield, rubber aprons, 
gloves, gum boots and helmets while handling  this chemical .  
6.2 Solid - Sodium hydroxide should be packed in mild steel drums of 24 gauges  or 
22 gauges . The container should be securely closed, the lid being tack -welded or 
expanded to a tight fit. If a closure is not air-tight, moisture and carbon dioxide  will be 
absorbed by sodium hydroxide. Over the lid, a prin ted sealing foil of tin should be 
affixed. On this label, it should be clearly stated that the container is carrying a 
corrosive and caustic chemical. Precautions regarding the handling and the 
corrosive nature of chemical should be clearly written on the container. It should also 
be marked with paint with the name of the manu facturer , grade and weight of caustic 
soda material, and the year and month of manufacture. The container use d for solid 
sodium hydroxide is generally not corrugated.  
6.3 Flakes - The mild steel drums used for flakes should be usually of 22 gauge 
black sheets and shou ld be corrugated for greater strength. The lid should be 
expanded into position or should be tack welded . All the other markings should be as 
for the solid drums. Both sol id and flake drums should be black painted.  
6.4 Lye - Lye of 50 or 73 percent strength should be transported in tankers. The 
tankers should b e generally painted in light grey or white with an alkali -resistant 
paint. The words 'caustic sod a 50% or 73 %’ sho uld be painted in large block letters 
horizontally across the tankers, on both sides. Precautio ns regarding the handling of 
the corrosive chemical shall be written on the label or on the painted tinplat e 
attached to the tanker, and should be prominently displayed. The words 
'CORROSIVE CHEMICAL' sho uld in addition b e engraved on both sides of the 
tanker . 
7 Preventive measures  
7.1Employee training - Workers required to handle sodium hydroxide in any form 
should be instructed about the hazards involved and safe methods of work. They 
should be provided with adequate and appropriate personal protective equipment 
and its correct use should be ensured. They should be instructed about basic first aid 
measures against alkali and the steps to be taken in the event of spillage of sodium 
hydroxide. They should be instructed about the location and use of showers, eye TBS/CDC -7 (5160 ) P3 
 
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 fountains, hose lines, etc. Food should not be stored or eaten in a work -area where 
sodium hydroxide is handled.  
7.2Medical examination - All new entrant s should be given a replacem ent medical 
examination before they are engaged in the manufacture of sodium hydroxide. All 
workers shoul d be regularly checked up by a physician with particular reference to 
dermatitis.  
7.3Personal protective equipment.  
7.3.1All personnel handling sodium hydroxide in any form should wear the following 
safety equipment:  
a) suitable closefitting  goggles with side shields.  
b) rubber or PVC gloves for the hands with protection to elbow. For handling,  molten 
and hot concentrated sodium  hydroxide (above 383 K), gloves made of asbestos 
lined inside with PVC or rubber are recommended. Health and safety precautions in 
handling gloves made with asbestos should be followed . 
c) non-slippery rubber gum boots or rubber -coated canvas boots.  
d) rubber apron.  
e) broad - brimmed alkali -resistant plastic or rubber hats to provide  protection for head, 
face and neck from splashing of sodium hydroxide.  
f) suitable respirators or protective hoods when handling flakes, granules or powdered 
sodium hydroxide.  
 
7.3.2  A ready accessible, - marked, quick -acting safety shower should be available 
in the area where sodium hydroxide is handled. Eye -washing fountain or a hose with 
a soft gentle flow of water should be readily available for eye irrigation. These and all  
safety equipment should be maintained in good working  
condition by periodic inspection and repair.  
7.4 Accident Investigation - All the accidents occurring in a sodium hydroxide plant 
should be thoroughly investigated to find out the causes of the accid ents and to 
suggest remedial measures and the detailed report should be recorded properly for 
future reference.  
 
8 First aid and medical treatment  
8.1General - Speed in removing sodium hydroxide from the affected parts is of 
primary importance. Whether a  fulltime physician is employed or not, industrial first 
aid kits should be kept at all places where sodium hydroxide is handled.  
8.1.1 Copious and prolonged application of water to affected part is of foremost 
importance. The irrigation should be continued  for as long as 1 to 2 hours. TBS/CDC -7 (5160 ) P3 
 
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 Contaminated clothing should be removed promptly. In case of severe burns and 
those involving extensive areas of body shock may ensure, and in this case, patient 
should be laid in a supine position and kept reasonably warm unt il the physician, 
who should be called in attendance at once, arrives. No oil or ointment of any kind 
should be applied within first 24 hours after exposure or subsequently without orders 
from the physician . 
8.1.2 Neutralization with acid or other chemicals  should be postponed until thorough 
washing has been done.  1% ammonium chloride or 3% boric acid solution is suitable 
for eye washing. 10% ammonium chloride or 2% acetic acid solution is suitable for 
application on skin.  
8.2Contact with eyes - Even if min ute quantities of sodium hydroxide either in solid 
or liquid form enter the eyes, they should be irrigated immediately with copious 
amounts of water for at least 15 min. Eyelids should be irrigated immediately with 
copious amounts of water for at least 15 min. Eyelids should be held" apart during 
washing. A physician preferably an eye specialist should be called at once and if 
necessary, eye washing may be continued for another 15 min. until he arrives. After 
the first washing, few drops of 3.5%  pinolcaine  solution or an equally effective 
aqueous topical anaesthetic may be instilled into the eyes. No oil or oily ointment 
should be used.  
8.3Ingestion - Do not attempt to induce vomiting. Patient should be encouraged to 
drink large amount of water. Dilute vinegar or a 5% solution of ammonium chloride 
may be administered freely if available. After dilution or neutralization of the alkali, 
white of egg or parathion oil may be taken for smoothing effect. Stomach tubes or 
emetics should not be used unless ordered by the physician.  
9 Disposal of empty containers and waste  
9.1Waste containing alkali is harmful to bacterial growth necessary for degra dation 
of organic waste. Such wastes should be properly treated and neutralized before it is 
led into sewers, rivers, ponds or open fields.  
9.2 Disposal of empty containers  
9.2.1  Empty flake drums should be thoroughly washed with water by filling to the 
brim, agitating and pouring out the water at least six times. Before washing, the drum 
should be visually examined to see that no appreciable quantities of caustic flakes 
are sticking inside.  
9.2.2  Solid drums are usually cut open, so the drum sheets shoul d be washed 
profusely with water before, disposal. In case the solid sodium hydroxide is dissolved 
out of the uncut drum, the empty drum should be treated like the empty flake drum 
before disposal.  TBS/CDC -7 (5160 ) P3 
 
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 9.2.3  In the case of returnable flake drums, care should be taken to tightly close and 
reseal the lid before returning the empty drums.