Gas-pak is a method used in the production of an

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

environment. It is used to culture bacteria which die or fail to grow in the presence of oxygen (''

anaerobes An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenate ...

''). These are commercially available, disposable sachets containing a dry powder or pellets, which, when mixed with water and kept in an appropriately sized

airtight A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers, but as technology advanced it applied to a larger categor ...

jar, produce an atmosphere free of elemental oxygen gas (O₂). They are used to produce an

culture in microbiology. "GasPak System". Accessed October 27, 2009. It is a much simpler technique than the

McIntosh and Filde's anaerobic jar McIntosh and Fildes' anaerobic jar is an instrument used in the production of an anaerobic environment. This method of ''anaerobiosis'' as others is used to culture bacteria which die or fail to grow in presence of oxygen ('' anaerobes''). It was ...

where one needs to pump gases in and out.

Constituents of gas-pak sachets

Sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds applica ...

- NaBH₄ # Sodium bicarbonate - NaHCO₃ #

Citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...

- C₃H₅O(COOH)₃ #

Cobalt chloride Cobalt chloride (cobalt paper) may refer to: * Cobalt(II) chloride Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula . The compound forms several hydrates ·''n'', for ''n'' = 1, 2, 6, and 9. Claims of the fo ...

- CoCl₂ (catalyst) The addition of a Dicot Catalyst may be required to initiate the reaction.

Reactions

*NaBH₄ + 2 H₂O = NaBO₂ + 4 H₂↑ *C₃H₅O(COOH)₃ + 3 NaHCO₃ + /nowiki>CoCl₂/nowiki> = C₃H₅O(COONa)₃ + 3 CO₂ + 3 H₂ + /nowiki>CoCl₂/nowiki> *2 H₂ + O₂ + /nowiki>Catalyst/nowiki> = 2 H₂O + /nowiki>Catalyst/nowiki>

Consumption of oxygen

These chemicals react with water to produce

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

along with

sodium citrate Sodium citrate may refer to any of the sodium salts of citric acid (though most commonly the third): * Monosodium citrate * Disodium citrate * Trisodium citrate The three forms of salt are collectively known by the E number E331. Applications ...

(C₃H₅O(COONa)₃) and water as byproduct

Again, hydrogen and oxygen reacting on a catalyst like

Palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...

ised alumina (supplied separately) combine to form water.

Culture method

The

medium Medium may refer to: Science and technology Aviation *Medium bomber, a class of war plane *Tecma Medium, a French hang glider design Communication * Media (communication), tools used to store and deliver information or data * Medium of ...

, the gas-pak sachet (opened and with water added) and an

indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health ...

are placed in an air-tight gas jar which is incubated at the desired

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

. The indicator tells whether the environment was indeed oxygen free or not. The chemical indicator generally used for this purpose is "chemical methylene blue solution" that since synthesis has never been exposed to elemental oxygen. It is colored deep blue on

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

in presence of atmospheric oxygen in the jar, but will become colorless when oxygen is gone, and anaerobic conditions are achieved.

References

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