Abstract Steam sterilisation indicator means for introducing into surgical and other materials to show that thorough penetration of the material by steam has been effected and that it has been exposed to the steam at an adequate temperature for an adequate time comprises a carrier on which is deposited a mixture of a carboxylic acid which loses carbon dioxide under steam sterilisation conditions together with one of its salts which on exposure to steam produces alkali and causes a continuous change of the pH value in the alkaline direction as exposure to steam continues, and a pH indicator deposited on the carrier and which will undergo changes in colour as the pH changes, to indicate the extent of exposure to steam which has occurred.
Indicator means as in claim 1, wherein the acid is 2,4-dihydroxybenzoic acid.
Claim 2
Dependent Claim
19 words
Indicator means as in claim 2, wherein the pH indicator consists of methyl red, bromo-cresol green and picric acid.
Claim 3
Dependent Claim
17 words
Indicator means as in claim 2, wherein the pH indicator consists of methyl red and bromothymol blue.
Claim 4
Dependent Claim
21 words
Indicator means as in claim 1, wherein the carrier is a piece of filter paper or fabric of a porous nature.
Claim 5
Dependent Claim
57 words
Indicator means as in claim 1, wherein the carrier having the mixture of a carboxylic acid and one of its salts and the pH indicator deposited thereon is enclosed in a transparent plastics envelope having sufficient permeability and thickness to retard penetration by steam and also prevent the materials deposited on the carrier from being washed away.
Claim 6
Dependent Claim
14 words
Indicator means as in claim 6, wherein the plastics envelope is formed of nylon.