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Safe Handling of

Caustic Soda(Sodium Hydroxide)

Japan Soda Industry Association

ContentsIntroduction 1 Information about Caustic Soda 2 1. Commercial Caustic Soda 2 2. General Characteristics of Caustic Soda 3 3. Effects of Caustic Soda on the Human Body 3 Containers for Caustic Soda 4 1. Kinds of Containers 4 2. Displays on the Containers 4 Handling of Containers 5 1. Transportation 5 2. Precautions for Storage 6 Tank Trucks, Rail Tanks, and Tankers 7 1. Structure 7 2. Unloading from Tank Trucks, Rail Tanks, and Tankers 7 Use of Caustic Soda 9 1. General Precautions 9 2. Methods for Dissolving 9 3. Treatment of Empty Containers and Waste 10 4. Accident Prevention Measures 11 5. Prevention Measures for Hygiene 12 Actions to be Taken in Case of a Leakage 12 Maintenance of the Facilities (Cleaning and Repairing) 13 Safety Facilities 14 Emergency Measures 15 1. Skin Exposure 15 2. Eye Exposure 15 3. Swallowing 16 Reference Items 16 1. Properties of Caustic Soda 16 2. Specific Gravity and Concentration of Caustic Soda Solution 17 3. Specific Gravity, Concentration, and Temperature of Caustic Soda Solution 18 4. Heat of Dissolution of Caustic Soda in Water 18 5. Phase Diagram for Caustic Soda 19 6. Boiling Point of Caustic Soda Solution 19 7. Specific Heat of Caustic Soda Solution 20 Related Laws and Regulations 21 Cases of Disasters 23










Caustic soda (excluding solutions containing not more than 5% caustic soda) is designated as a deleterious substance under Japanese laws, and is a strongly corrosive substance. Persons who handle caustic soda should learn about related laws and regulations (such as the Poisonous and Deleterious Substance Control Law), its properties, and precautions on handling; and should observe them to ensure safety. This leaflet compiles the information that dealers, transporters, and consumers handling caustic soda need to know as a guideline for the routine prevention of accidents.


I. Information about Caustic Soda1. Commercial Caustic SodaCommercial caustic soda is classified into solid types and liquid types according to its phases as well as into industrial, reagent, and Japanese Pharmacopoeia grades according to its uses. Of the solid types of commercial caustic soda, flaked caustic soda is also a commercial product. The types of solid caustic soda are as shown in the following table, and the qualities and testing methods are specified in JSIA (Japan Soda Industr y Association) Standards, JIS (Japanese Industrial Standards), the Japanese Pharmacopoeia and the JSFA (Japanese Standards for Food Additives). Quality of caustic soda Grade Industrial caustic soda Reagent grade caustic soda Pharmacopoeial caustic soda Type Liquid, type 1, type 2 Solid, type 1, type 2 Special grade, class 1 Quality JSIA-01 JSIA-02 JIS K 8576 Japanese Pharmacopoeia Testing method Testing method JIS K 1200 JIS K 1200

NaOH 95.0%

Quality of caustic soda for food additives (JSFA) Purity Form Crystalline caustic soda: 70 75% Caustic soda, anhydrous: 95% Crystalline grade: White crystalline powder or granules Anhydrous grade: White spherical shapes, flakes, rods, or other solid forms; white powder Colorless, substantially transparent 2% 4 g/g as As2O3 30 g/g as Pb 0.1 g/g as Hg 2

Dissolved state Sodium carbonate content Arsenic content Heavy metal content Mercury content

2. General Characteristics of Caustic SodaCaustic soda is the most typical of the strong alkalis. Although there is no danger of it exploding or igniting, it reacts with various acids, such as hydrochloric acid, and is neutralized and generates considerable exothermic heat of neutralization. It corrodes metals, such as aluminum, tin, and zinc. During this process, it generates hydrogen, which has the potential to behave as an explosive gas. It is highly hygroscopic, and absorbs the moisture, carbon dioxide, or sulfur dioxide in the air. It is also highly deliquescent and absorbs moisture to form an aqueous solution. When liquid caustic soda is diluted, it generates a considerable amount of heat of dilution. Since this rapidly generates strong heat and the resulting solution may spatter if the water is carelessly poured into it, care must be taken. Caustic soda easily decomposes animal fibers. Although plant fibers are also decomposed, they have a higher resistance than animal fibers. Although materials resistant to corrosion by caustic soda include stainless steel, steel-epoxy resins, and fiber-reinforced plastics, steel and rubber-lined steel are the most frequently used.

3. Effects of Caustic Soda on the Human BodyAlkalis have a decomposing effect on proteins, which may gradually penetrate the deep tissues unless the adhered alkali is completely removed. In particular, if the eyes are exposed to an alkali, since eye tissue is rapidly affected causing a lowering or loss of vision, great care should be taken. Even a dilute solution can affect the tissue of the skin if it repeatedly comes into contact with the skin, which may cause dermatitis or chronic eczema. If the concentration of the solution is high, the affected tissue rapidly decomposes. If the solution is swallowed by mistake, it causes inflammation in the mouth, 3

throat, esophagus, or stomach. The inhalation of caustic soda dust or mist causes various degrees of injury in the respiratory tract. Thus, the allowable concentration of caustic soda dust or mist in the air in a working area is specified as 2 mg/m3 (upper limit).

II. Containers for Caustic Soda1. Kinds of ContainersSolid caustic soda is contained in thin steel drums. Flake caustic soda is contained in drums or PVC-lined paper bags as shown in the table.No. 1 2 3 4 5 Outer diameter (mm) 575 450 235 400 Length:700 Width: 400 Height (mm) 900 735 375 550 100 Outlet (mm) 403 326 125 395 Machine sewn Total weight (kg) 174 83 16 53.5 25.3 Tare weight (kg) 24 8 1 3.5 0.3 Net weight (kg) 150 75 15 50 25 Drum Fiber drum PVC-lined paper bag Name

Liquid caustic soda is contained in rectangular cans or drums. For the transportation of a large quantity of liquid caustic soda, tank trucks, rail tanks, or tankers are used. Reagent-grade caustic soda is contained in glass bottles.

2. Displays on the ContainersThe Poisonous and Deleterious Substances Control Law requires the following to be displayed on the containers: Container (outside):No Medical Use and Deleterious Substance 4

(red characters on a white background) Name, grade, net weight of the contents Name and address of the manufacturer or importer Tank truck: Poison (white characters on a black background) (On the front and back of the truck)

On both sides of rail tanks, Exclusive Use for Caustic Soda is displayed. Care must also be taken to the display requirements of other related laws and regulations.

III. Handling of Containers1. Transportation(1) General precautions Close the lid or cover of the container so that it is airtight in order to avoid moisture absorption during transportation. For transportation in drums, use boxcars, but if gondola cars are used, cover the drums with sheets. In the case of consolidated transport, keep acids away from the caustic soda, and do not place the containers of caustic soda on top of other containers containing organic chemicals. Since crystals are precipitated from liquid caustic soda when the temperature lowers, do not expose it to low temperatures for a long period of time. The freezing point of standard commercial liquid caustic soda is 512 When solid caustic soda is being handled directly, or liquid caustic soda is being handled, be sure to wear protective goggles and rubber gloves, and wear rubber boots or rubber clothing as required.


Dispose of items contaminated by ambient caustic soda mist, or that have been soaked in liquid caustic soda, after treatment to make them harmless. Since caustic soda generates heat when it is diluted by water or neutralized by an acid, and may form a mist, make sure the eyes or skin are not exposed to the mist. (2) Transportation of caustic soda by tank truck The laws require that each tank truck be provided with a document describing the name, components and grade of the contents, and the first aid measures to be taken in case of an accident, protective equipment, tools, and so on. In the case of long period of transportation, a standby driver is required to ride in the truck. The driver must be certain to close the manholes or valves so that the liquid does not leak. (3) Transportation of caustic soda by ship When caustic soda is transported by ship, refer to the Ship Safety Law.

2. Precautions for Storage Caustic soda is specified by the Poisonous and Deleterious Substances Control Law as a non-medical deleterious substance. Therefore, the characters for No Medical Use and the red characters for Deleterious Substance on a white background, as well as a description of the contents and their constituents must be displayed on the tank. In addition, the storage place must have measures to secure it against losses or theft (locking), and preventive measures to control splash, leakage, outflow or penetration to the external environment must also be taken. In storage areas, caustic soda must be stored separate from other chemicals. In anticipation of any breakdown of the containers, caustic soda must be isolated from acids, metals, explosives, organic peroxides and so on.


When caustic soda is stored in steel drums, store it in a warehouse or indoor stock yard that is as dr y as possible to prevent the external corrosion of drums, moisture absorption, and freezing. Although the tank for the caustic soda solution can be a steel tank, it is safer to use other


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