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Code: BR0048

* Due to the low ionic content of this medium no pH is specified.
One tablet makes 500ml of quarter-strength Ringer containing 0.05% of sodium thiosulphate.

Directions
To prepare quarter-strength Ringer Solution containing thiosulphate, dissolve 1 tablet in 500ml distilled water. Sterilise by autoclaving at 121°C for 15 minutes.

Description
Oxoid Thiosulphate Ringer Tablets are formulated to provide, after the addition of distilled water, a Ringer Solution (British Pharmacopoeia¹) containing 0.05% of sodium thiosulphate hydrate. Use of the B.P. Ringer instead of the Ministry of Health Ringer ensures chemical stability without altering the physiological properties of the diluent.

The purpose of the sodium thiosulphate is to neutralise residual chlorine present in bacteriological samples and rinses as a result of the previous use of gaseous chlorine or chlorine-containing disinfectants. The thiosulphate immediately terminates the bactericidal action of the chlorine in the sample - so that subsequent bacteriological examination more accurately indicates the pollution of the sample at the time of collection. Sterile Thiosulphate Ringer Solution is consequently employed for rinse water samples taken for sanitary tests (from equipment and pipe lines, etc.) where a chlorine-containing cleansing fluid has been used. Davis used a Ringer Solution with added sodium thiosulphate, as a rinse after the use of sodium hypochlorite². Egdell et al.³ employed a Thiosulphate Ringer Solution in their bacteriological studies of immersion cleaned milking equipment.

Also see:
BR0049     Calgon Ringers Tablets
BR0052     Ringers Solution Tablets

Technique
100ml of prepared solution will completely neutralise 7mg of chlorine. Oxoid Thiosulphate Ringer Tablets may be used in the assessment of the cleanliness and sterility of dairy plant, after hypochlorite solution has been used for disinfection purposes (see Davis²). The methods described by Davis rely on swabbing or rinsing of apparatus or milk bottles. In reference to the swab method, see `Calgon’ Ringer Tablets.

References
1 British Pharmacopoeia (1953) p 501.
2 Davis J. G. (1956) `Laboratory Control of Dairy Plant’. Dairy Industries Ltd., London.
3 Egdell J. W., Lomax K. L., Adams R. P. and Aitken M. J. (1958) J. Appl. Bact. 21(1). 109-117.