US3898172A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Irreversible humidity indicator
Assignee: United States Department of Energy
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Filing: 1973-05-03
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Granted: 1975-08-05
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Expires: 1993-05-03
Abstract
Abstract Particles of colored dye are distributed over the surface of a dry, deliquescent salt having a neutral color. When exposed to a humidity level above that which causes deliquescence of the salt, the dye bleeds through and imparts its developed tincture to the resulting saturated salt solution. On dehydration, the dye remains infused throughout the dried salt to present an irreversible indication of the humidity exposure.
Inventors
- 👤 Robert B Reif
- 👤 Philip F Kurz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 00:43
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/75; G01N21/77; G01N21/78; G01N21/81; C; C09; C09B; C09B67/00; C09B67/0097; G01N31/00; G01N31/22; G01N31/222; Y; Y10; Y10S; Y10S252/00; Y10S252/963
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
95 words
IN A HUMIDITY INDICATOR CONSISTING ESSENTIALLY OF A COMBINATION OF A WATER-SOLUBLE DYE AND A DELIQUESCENT SALT DISPOSED ON A MOISTURE-IMPERVIOUS, FUSED SUBSTRATE, THE IMPROVEMENT WHEREIN SAID DELIQUESCENT SALT, BEING IN DRIED STATE, IS ADHERENTLY DISPOSED DIRECTLY ON SAID FUSED SUBSTRATE, AND SAID WATER-SOLUBLE DYE, CHARACTERIZED BY EXHIBITING A RECONGNIZABLE COLOR DEVELOPMENT ON DISSOLUTION, IS DISTRIBUTED AS FINE TRY DYE PARTICLES DIRECTLY ON OUTWARDLY FACING SURFACES OF SAID DRIED SALT TO PROVIDE AN IRREVERSIBLE COLOR CHANGE ON EXPOSURE TO RELATIVELY HUMIDITY LEVELS OF BETWEEN ABOUT 6 AND 20% AT AMBIENT TEMPERATURES AT WHICH SAID DELIQUESCES.
Claim 2
Dependent Claim
95 words
IN A HUMIDITY INDICATOR CONSISTING ESSENTIALLY OF A COMBINATION OF A WATER-SOLUBLE DYE AND A DELIQUESCENT SALT DISPOSED ON A MOISTURE-IMPERVIOUS, FUSED SUBSTRATE, THE IMPROVEMENT WHEREIN SAID DELIQUESCENT SALT, BEING IN DRIED STATE, IS ADHERENTLY DISPOSED DIRECTLY ON SAID FUSED SUBSTRATE, AND SAID WATER-SOLUBLE DYE, CHARACTERIZED BY EXHIBITING A RECONGNIZABLE COLOR DEVELOPMENT ON DISSOLUTION, IS DISTRIBUTED AS FINE TRY DYE PARTICLES DIRECTLY ON OUTWARDLY FACING SURFACES OF SAID DRIED SALT TO PROVIDE AN IRREVERSIBLE COLOR CHANGE ON EXPOSURE TO RELATIVELY HUMIDITY LEVELS OF BETWEEN ABOUT 6 AND 20% AT AMBIENT TEMPERATURES AT WHICH SAID DELIQUESCES.
Claim 3
Dependent Claim
94 words
The humidity indicator of claim 1 wherein a plurality of the discrete salt-dye combinations are disposed on said substrate, each of said combinations having a deliquescent salt with a propensity to liquefy at a minimum humidity level other than the minimum humidity level effective to liquefy salts within other of said plurality of discrete salt-dye combinations, whereby said humidity indicator is capable of permanently recording the occurrence of a maximum humidity level as being between the humidity levels that cause deliquescence in those salts that have liquefied and those salts that have not liquefied.
Claim 4
Dependent Claim
55 words
The humidity indicator of claim 2 adapted to determine relative humidity levels of 7-14% at ambient temperature wherein three discrete said salt-dye combinations are disposed on said substrate, said salt-dye combinations consist of ZnCl2 - C. I. Acid Violet 19, ZnBr2 - C. I. Acid Violet 19 and LiCl - C. I. Acid Violet 19.
Claim 5
Dependent Claim
52 words
The humidity indicator of claim 1 having a fused glass substrate with a nonabsorbent surface, said surface including a roughened portion treated with a wetting agent for receiving a layer of said deliquescent salt, and said water-soluble dye having the form of discrete particles distributed over the surface of said salt layer.
Claim 6
Dependent Claim
56 words
The humidity indicator of claim 1 wherein said deliquescent salt is selected from the group of neutral-color salts consisting of LiI, LiCl, LiBr, ZnI2, ZnCl2 and ZnBr2 and said dye is selected from the group of triarylmethane dyes consisting of C. I. Acid Violet 19, C. I. Acid Blue 1 and C. I. Acid Blue 9.
Claim 7
Dependent Claim
58 words
A method of preparing the humidity indicator of claim 1 comprising: dissolving said salt in liquid to form a solution, applying said film of said solution on the surface of a substrate, evaporating said film to dryness, thus leaving a dried salt residue on said substrate, and sprinkling particles of dry, water-soluble dye over said dried salt residue.
Claim 8
Dependent Claim
48 words
The method of claim 6 including the steps of roughening said surface of the substrate and treating the roughened surface with a wetting agent prior to applying said film of salt solution thereon in order to enhance the adherent qualities of said dried salt residue to said substrate.
Claim 9
Independent Claim
145 words
A method of determining the occurrence of a humidity level comprising: applying a film of deliquescent salt solution onto a nonabsorbent, fused substrate; evaporating said salt solution to dryness to form a dried salt layer adhering to said fused substrate; said dried salt consisting essentially of said deliquescent salt having a propensity to liquefy at between about 6 and 20% relative humidity at ambient temperatures and above said humidity level and being of neutral color in both liquid and solid form; sprinkling the surface of said dried salt with dry, water-soluble dye particles characterized by exhibiting a recognizable color development on dissolution to form a heterogeneous salt-dye combination on said substrate; exposing said salt-dye combination to said humidity level to form a liquid solution of said salt uniformly infused with the tincture of said dye whereby the occurrence of said humidity level is irreversibly determined.
Claim 10
Independent Claim
145 words
A method of determining the occurrence of a humidity level comprising: applying a film of deliquescent salt solution onto a nonabsorbent, fused substrate; evaporating said salt solution to dryness to form a dried salt layer adhering to said fused substrate; said dried salt consisting essentially of said deliquescent salt having a propensity to liquefy at between about 6 and 20% relative humidity at ambient temperatures and above said humidity level and being of neutral color in both liquid and solid form; sprinkling the surface of said dried salt with dry, water-soluble dye particles characterized by exhibiting a recognizable color development on dissolution to form a heterogeneous salt-dye combination on said substrate; exposing said salt-dye combination to said humidity level to form a liquid solution of said salt uniformly infused with the tincture of said dye whereby the occurrence of said humidity level is irreversibly determined.
Claim 11
Dependent Claim
94 words
The method of claim 8 adapted to measure relative humidities below about 20% wherein said step of evaporating said deliquescent salt solution to dryness is performed at about 130*C. and 6% relative humidity; said deliquescent salts being selected from the group of natural-color salts which deliquesce at below about 20% relative humidity consisting of LiI, LiCl, LiBr, ZnI2, ZnCl2 and ZnBr2 and said water-soluble dye particles being selected from the group of colored triarylmethane dye particles consisting of C. I. Acid Violet 19, C. I. Acid Blue 1 and C. I. Acid Blue 9.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-04 | 1979-02-03 | 1979-08-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-04 | 1983-02-03 | 1983-08-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-04 | 1987-02-03 | 1987-08-05 | $7700.00 | Window Closed / Lapsed |