Reversible detector for gaseous carbon dioxide

• US 5,846,836 A
• Filed: 10/29/1996
• Issued: 12/08/1998
• Est. Priority Date: 06/06/1990
• Status: Expired due to Term

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Mallow, William A.
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US08/739,324
• Time in Patent Office: 770 Days
• Field of Search: 436/133, 436/167, 436/169, 422/56-61, 128/207.14
• US Class Current: 436/169
• CPC Class Codes: G01N 31/22 using chemical indicators G01N31/02 takes precedence
• CPC Class Codes: G01N 31/223 for investigating presence of specific gases or aerosols G01N31/221, G01N31/222 take precedence; actuation of fire alarm by presence of smoke or gases G08B17/10
• CPC Class Codes: G01N 33/004 for CO, CO2
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y10T 436/204998 Inorganic carbon compounds

Abstract

An apparatus and method for visually and continuously monitoring gaseous concentrations of electrophiles such as carbon dioxide. A coating composition comprising an organic binder, filler/pigment, an activator, and carbon dioxide sensitive color indicator interacts with a primed substrate to which it is applied for support. The coated primed substrate may then be used for estimation of carbon dioxide concentration by the detection of a substantially instantaneous and reversible color change of the coated primed substrate.

Claims

1. An indicator substrate to be coated with a coating composition to make a reversible color carbon dioxide detector, the indicator substrate being made by a process comprising

preparing an indicator solution comprising a solvent and a dye component, said dye component being present in said solvent at about 10% concentration by weight;

said solvent being prepared by mixing about equal parts by volume of acetone, ethanol, diethyl ether and acetonitrile; and

said dye component being prepared by mixing about 50% by weight of N-methyl-4-(phenylazo)benzenamine, with about 50% by weight of a mixture prepared from approximately equal parts by weight of the following dyes;

o-cresolsulfonephthalein (Cresol-Red),

thymolsulfonaphthalein (Thymol-Blue),

p-benzenesulfonic-azo-dimethylaniline (Methyl-Orange),

o-carboxybenzene-azo-dimethylaniline (Methyl-Red),

amino-dimethyl amino-toluphenazonium chloride (Neutral-Red),

benzene-azo-dimethyl-amine (Methyl-Yellow),

2,4,6-trinitrophenyl-methyl-nitro amine,

p-nitro benzene-azo-salicylic acid (Alizarin-Yellow), and

thymolphthalein; and

applying said indicator solution to a porous substrate comprising pH neutral material to make an indicator substrate to be coated with a coating composition to make a reversible color carbon dioxide detector.