(19) &   

(11) EP 1 058 113 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: G01N 31/22 (2006.01) G01N 21/78 (2006.01) 18.03.2009 Bulletin 2009/12

(21) Application number: 00201783.8

(22) Date of filing: 19.05.2000

(54) Method for quantifying molybdate in absorption refrigeration system brines Verfahren zur Quantifizierung von Molybdaten in Salzlaugen für Absorptionskälteanlagen Procédé pour la quantification de molybdate dans les saumures de réfrigérateurs à absorption

(84) Designated Contracting States: • Tang, Xia DE ES FR GB IT West Hartford, Connecticut 06119 (US) (30) Priority: 02.06.1999 US 324376 (74) Representative: Booth, Catherine Louise et al (43) Date of publication of application: Frank B. Dehn & Co. 06.12.2000 Bulletin 2000/49 St Bride’s House 10 Salisbury Square (73) Proprietor: CARRIER CORPORATION London Farmington, EC4Y 8JD (GB) Connecticut 06034-4015 (US) (56) References cited: (72) Inventors: US-A- 5 106 581 US-A- 5 744 365 • Condit, David A. Avon, • PATENT ABSTRACTS OF JAPAN vol. 1996, no. Connecticut 06001 (US) 08, 30 August 1996 (1996-08-30) & JP 08 105835 • Jaworowski, Mark R. A (NIPPON CHEM IND CO LTD), 23 April 1996 Glastonbury, (1996-04-23) Connecticut 06033 (US)

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 058 113 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 1 058 113 B1 2

Description inhibiting performance of the fluids being superior to lith- ium chromate inhibitors. This improved system of corro- [0001] This invention relates generally to absorption sion inhibitors is described in greater detail in US Patent refrigeration systems. More particularly, the invention re- 5,547,660 for Absorption Refrigeration System working lates to diagnostics for absorption refrigeration systems. 5 Fluid with Molybdate, Borate, Silicate Inhibitor Blend by More particularly still, the invention relates to a method Downey and assigned to Carrier Corporation. Moreover, and apparatus for performing diagnostics on a corrosion this improved system of corrosion inhibitors is employed inhibitor present in absorption refrigeration systems. in the WB-1 inhibited LiBr absorption chillers manufac- [0002] There are a number of different pairs of refrig- tured and sold by Carrier Corporation. erants and absorbents that are used in absorption refrig- 10 [0006] The aforementioned WB-1 inhibited LiBr ab- eration systems. One such pair is water and a halogen sorption chiller of the Carrier Corporation uses an aque- salt of , such as , ous solution of water and a lithium halide, specifically or mixed to form a concentrated aqueous lithium bromide (LiBr), as the working fluid (sometimes solution of the lithium salt. Another such pair is water and termed "brine"), and employ a further solution of lithium 15 ammonia. molybdate (Li2MoO4), lithium borate and lithium silicate [0003] Iron and iron alloys like steel and copper and as the corrosion inhibitor. Although the lithium borate and copper alloys are typical construction materials used in lithium silicate inhibitors remain in solution in the aqueous absorption refrigeration systems. Corrosion of these ma- working fluid in adequate quantities throughout the life terials can cause difficulties. Not only is metal loss of of the fluid system, the same may not be so with respect concern but also the oxidation of ferrous metal can be 20 to the molybdate inhibitor. The lithium molybdate is only accompanied by evolution of gaseous hydrogen. If not sparingly soluble in the LiBr brine, and must be main- purged, the hydrogen can interfere with the proper oper- tained in the 100-200 ppm range to assure the desired ation of the system. Corrosion is of particular concern in action as a corrosion inhibitor. However, during start-up systems that use halogen salts of lithium. And regardless and/or during other times of stress on the refrigeration of the refrigerant/absorbent pair used in a particular sys- 25 system, the molybdate inhibitor may become sufficiently tem, metal corrosion rates increase as system tempera- depleted as to take it below the preferred concentration tures increase. range and thus expose the system to corrosion problems. [0004] It is well known in the prior art that the addition [0007] To minimize the risk of corrosion problems of a salt of chromium, such as lithium chromate, to the which may result from an insufficient concentration of the refrigerant/absorbent solution in an absorption refriger- 30 molybdate inhibitor, it has been the practice to obtain ation system, is effective in reducing metallic corrosion. samples of the LiBr brine in the field at the site of the The presence of the chromate compound promotes the absorption refrigeration system and to then send them formation of a protective layer of iron and chromium ox- to another location for analysis. That analysis is typically ides on the surfaces of the system that are in contact with performed by a non-portable, relatively expensive tech- the absorbent. With a decrease in iron oxidation, there 35 nique and equipment, such an inductively coupled plas- is also a corresponding decrease in the production of ma-atomic emission spectroscopy (ICP-AES). This proc- noncondensible hydrogen. There is some concern, how- ess occasions undesirable delays (measured in days) ever, about the health risks that chromium presents. At and significant monetary costs. Although various types least one government authority, the U.S. Environmental of on-site analyzers and analysis techniques have been Protection Agency, has identified chromium as a carcin- 40 employed for monitoring the level of chromate inhibitor ogen, and has prohibited the presence of chromium com- concentrations, including color comparators and spec- pounds in systems that are open to the atmosphere. Ab- trometers, those techniques as they presently exist are sorption refrigeration systems are, of course, closed sys- not suitable for determining molybdate concentrations. tems, but a certain amount of working fluid from the sys- Similarly, existing analytical processes for determining tem can become exposed to the atmosphere through the 45 concentrations of molybdate in refrigeration systems are taking of samples, the manufacturing process and spills operative if the working fluid is water, but not if it contains during handling and filling. And, at the end of the service a lithium halide brine, such as lithium bromide. Other prior life of a system, the system charge will necessarily re- art systems for measuring molybdate ions in a refrigerant quire disposal of the working fluid, including the chromi- are disclosed in JP 08105835, in which multiple steps um compounds that it contains. 50 are carried out including forming a turbid solution and [0005] To address the foregoing concern, there has using thioglycolic acid, and in US 5106581, in which the recently been developed a chromium-free aqueous so- use of test strips having dithiol or thyocyanate and tin lution, typically of a halogen salt of lithium, for use as a chloride in the presence of acid for detecting molybdate working fluid in an absorption refrigeration system. In ad- ions is discussed. dition, the solution also contains a compound containing 55 [0008] Accordingly, there is a need for determining mo- a molybdate, a compound containing a borate and per- lybdate inhibitor concentrations in lithium halide brines haps also, a compound containing a silicate. The added using a method and/or apparatus which facilitates on- constituents act as effective corrosion inhibitors, with the site analysis. The method and apparatus for making such

2 3 EP 1 058 113 B1 4 on-site analysis should be relatively portable and eco- tometer is field calibrated using a brine sample having a nomical, and provide rapid and accurate determination known concentration of molybdate inhibitor, typically ze- of molybdate inhibitor concentration. ro, to establish a reference. For a lithium bromide brine, [0009] The present invention provides a method and the selected reagent is stannous chloride in hydrochloric apparatus for making a rapid and accurate analysis of 5 acid, and the resulting characteristic color corresponds the concentration of molybdate inhibitor in a lithium halide to a wavelength in the range of 520-580 nm, typically brine at the site of a refrigeration system containing the pink with a maximum near 550-560 nm. brine. The analysis may be performed using relatively [0014] Fig. 1 is a spectral plot of the absorbance spec- standard, portable equipment in a non-complex manner. trum of a lithium bromide brine, treated with a reagent, [0010] In accordance with the present invention, there 10 for differing concentrations of included lithium molybdate is provided a method of quantatively analyzing molybdate inhibitor. inhibitor as claimed in claim 1. In its preferred embodi- [0015] Fig. 2 is a graphical plot of the spectral absorb- ments at least, there is provided a method for quantita- ance at 550 nm for different concentrations of lithium mo- tively analyzing molybdate inhibitor in a lithium bromide lybdate in lithium bromide brine, showing the generally brine, typically at the side of a refrigeration system con- 15 linear relationship. taining the brine. The system comprises reagent means [0016] Fig. 3 is a generalized functional block diagram and a means for determining molybdate concentration of a spectrophotometer for use in the analytical system based on color analysis. The reagent means is mixed and process of the invention. with a sample of the lithium halide brine having an un- [0017] The present invention recognizes that a partic- known concentration of molybdate inhibitor, and is se- 20 ular reagent, when mixed with a lithium halide brine, be- lected to create a characteristic color of the sample ing lithium bromide, containing a lithium molybdate cor- caused by the presence of the molybdate inhibitor, the rosion inhibitor, will provide a particular colorimetric re- intensity of that color also being a function of the concen- sponse which is accurately indicative of the concentration tration of the molybdate inhibitor. The reagent means of the molybdate inhibitor. This recognition is extended may be an acidified reducing agent or a separate acid 25 and applied to the utilization of portable, economical di- and reducing agent, selected to produce a stable color agnostic equipment for making on-site determinations of change, and does so through a pH adjustment and a molybdate inhibitor concentrations in absorption refrig- redox reaction. A spectrophotometer responsive to the eration systems. optical wavelength of the characteristic color of the sam- [0018] In accordance with the invention, a represent- ple is a preferred means for indicating the presence of 30 ative refrigeration system (not shown) employs an aque- molybdate inhibitor in the brine sample. The spectropho- ous solution of water and a lithium halide, being lithium tometer is also responsive to the intensity of that color to bromide LiBr, as the working fluid, or brine, in the absorp- provide an indication of the concentration of the molyb- tion chiller. The concentration of LiBr in the brines is typ- date inhibitor in the sample. A color comparator provides ically in the range of 50-60%, and in the present embod- an alternate means for determining the molybdate con- 35 iment about 55%. The refrigeration system further em- centration. ploys a solution of lithium molybdate Li2MoO4, lithium [0011] In a representative refrigeration system in borate and lithium silicate as the corrosion inhibitor. The which the brine is lithium bromide, the selected reagent lithium molybdate is only sparingly soluble in the LiBr is stannous chloride Sn(II)Cl2 in hydrochloric acid HCl brine and must be maintained in the 100-200 ppm range 40 (aq), and the resulting characteristic color of the sample to assure the desired function as a corrosion inhibitor. containing the molybdate inhibitor absorbs visible light in [0019] To monitor the level or concentration of lithium the range of 520-580 nm, and more particularly is a pink molybdate inhibitor in a rapid, accurate and convenient color which absorbs visible light with a maximum near manner at the site of the refrigeration system, a system about 550-560 nm. The spectrophotometer may be a and method have been developed which permit the use hand-held colorimeter operative only near about 550 nm. 45 of portable, hand-held analytical instruments to provide [0012] The process of the invention includes obtaining such measurements. It has been discovered that a rea- a sample of the lithium halide brine containing the un- gent which is an acidified reducing agent, when mixed known quantity of molybdate inhibitor, mixing a selected and reacted with a sample of LiBr brine having a molyb- reagent with that sample to provide a characteristic color, date inhibitor present in an unknown concentration, will analyzing the sample to determine the presence and op- 50 create a characteristic color in the mix which indicates, tical intensity of that characteristic color, and providing by its presence and optical intensity, the presence and an indication of the concentration of molybdate inhibitor concentration of molybdate inhibitor. A suitable portable in the brine sample as a function of the determined pres- spectrophotometric instrument or other device is then ence and intensity of the characteristic color. used to make the quantitative determinations. The rea- [0013] The analysis of the sample is conducted spec- 55 gent is chosen to provide the characteristic color without trophotometrically, preferably using a portable spectro- interfering with the optical detection of the characteristic photometer or colorimeter responsive to the optical color. wavelength of the characteristic color. The spectropho- [0020] A one-step acidification and reduction reaction

3 5 EP 1 058 113 B1 6 uses, as a reagent, stannous chloride SnCl2 in hydro- spectrophotometers or colorimeters adapted for use at chloric acid HCl (aq), to reduce molybdenum and form a or near the 550 to 560 nm wavelength range. Moreover, pink color in the visible spectrum range between about the slope or sensitivity of the relationship is great enough 520 and 580 nm (nanometers). More specifically, the par- to provide adequate discrimination to a measuring instru- ticular reaction is believed to involve the reduction of Mo 5 ment. The absorbance characteristic of Fig. 2 was de- (VI) (Li2MoO4) to Mo(III) under acidic conditions. The re- picted at 550 nm, which is a convenient, commercially 3- sulting complex is believed to be [MoX6] or [MoX5 available system. However, the peak response is closer 2- - - (H2O)] where X = Br or Cl . Those complexes typically to 560 nm, and a steeper slope is possible at that wave- possess a characteristic color of red, or more accurately length if increased sensitivity is required. pink, in the 550-560 nm range of the visible spectrum. 10 [0024] Referring to Fig. 3, there is depicted, in block The reaction occurs at room temperature and reaches diagram form, a spectrophotometric instrument capable completion within 10 minutes. Moreover, the developed of making the analytical measurements of the present color remains stable for at least 48 hours at room tem- invention. The spectrophotometric instrument, typically perature, provided the reducing agent, SnCl2 or SnBr2 a spectrophotometer or colorimeter 10, includes a radi- has not been depleted. Importantly, soluble copper, a 15 ation source 12; a dispersive device or a filter 14; a sam- common contaminant in used brine, does not interfere ple holder, or cell, 16; a detector 18, such as a photo at concentrations up to about 500 ppm. The concentra- detector and amplifier; and a readout system 20. The tions of copper in used brine are typically less than 500 sample 16, as represented in broken line 16’, may be ppm. Similarly, no other contaminants in used brines prepared separately and subsequently inserted into the were found to interfere with the desirable characteristics 20 spectrophotometer 10. of this particular reagent and its reaction with molybdates. [0025] In accordance with the invention, the spectro- [0021] Reference is made to Fig. 1, which depicts the photometer 10 is preferably and typically portable, and (optical) absorbance of the LiBr brine and the included may be hand-held during use on-site. The HACH Generic lithium molybdate, lithium borate and lithium silicate in- Pocket Portable Colorimeter, manufactured and sold by hibitors of the WB-1 inhibitor complex that has been treat- 25 HACH Company of Loveland, Colorado is relatively small ed with the reagent. Particular notice should be taken of and portable, thus being readily useable for on-site anal- the absorbance do to the reduced molybdenum complex ysis of molybdate concentrations in absorption refriger- in the general region of 500-600 nm. More specifically, ation systems. Moreover, the HACH colorimeter 10 af- in the region from about 520 to 580 nm, the intensity of fords the accuracy and economy required or desired of the absorbance is seen to be significantly elevated as a 30 such an instrument. The colorimeter 10 is selected to be function of the concentration of the molybdate inhibitor. responsive substantially only in the optical range of in- The maximum absorbance occasioned by the presence terest, in this instance about 550 or 560 nm wavelength. of molybdate appears in the region of about 550 to 560 The colorimeter 10 used herein was responsive at the nm, and is characterized as a pink color. 550 nm wavelength. [0022] Referring further to Fig. 1 in the spectral region 35 [0026] In use, the analytical process of the invention between about 500 and 600 nm, there is depicted the was practiced using the HACH Portable Colorimeter 10 absorbance of the LiBr brine for various concentrations according to the following procedure. The colorimeter 10 of lithium molybdate inhibitor reacted with the SnCl2 in is precalibrated for the measurement of molybdate con- HCl (aq). The concentrations of molybdate range from 0 centrations in 50-60% LiBr brines having the WB-1 cor- ppm to 200 ppm, as indicated on the several spectral 40 rosion inhibitors (lithium molybdate, lithium borate and scans in that region. It will be noted that the presence of lithium silicate). This precalibration incorporates the molybdate is readily discernible, even in relatively small slope of the relationship depicted in Fig. 2. The reagent concentrations, by the characteristic rise in the absorb- for reacting with the molybdate inhibitor is 0.3M SnCl2 in ance in the region of 520 to 580 nm, and particularly at 6N HCl (aq). A further sample of uninhibited (no corrosion the maximum region of about 550 to 560 nm. Also im- 45 inhibitor) LiBr brine (50% or above) is also provided as portant is the generally linear relationship existing be- a reference sample (blank). The field calibration proce- tween the concentration of molybdate and the optical ab- dure includes the following steps: sorption characteristic at the wavelength region of inter- est. In Fig. 1, the absorbencies for molybdate concentra- - Use a 5 or 10 mL syringe to measure 10 mL of un- tions of 0, 25, 50, 100, 150 and 200 ppm are depicted, 50 inhibited LiBr brine into a sample bottle (cell). Name thus covering the range of interest for concentrations of this solution as "blank." molybdate dissolved in the LiBr brine. - Use a 5 or 10 mL syringe, with a 1.0 Pm filter at- [0023] Referring to Fig. 2, there is graphically depicted tached, to deliver 10 mL of each sample solution of the optical absorbance characteristic for the reacted mo- "unknown" molybdate concentration into a separate lybdate at about 550 nm as a function of the molybdate 55 cell. The filter removes particulate to provide a clear concentration in the 55% LiBr brine. This emphasizes solution. the general linearity of the relationship, thus facilitating - Add 1 mL of molybdate reagent into the cells con- the use of absorption spectroscopy, and particularly taining blank and unknown sample solutions.

4 7 EP 1 058 113 B1 8

- Cap each cell tightly and mix. (aq), with a sample to create a characteristic col- - Wait for 10 min to allow the color to fully develop. our of the sample in the presence of molybdate - Insert the cell containing blank solution (uninhibited inhibitor, the intensity of the characteristic color LiBr) into the sample cell compartment of the HACH being a function of the concentration of molyb- colorimeter with the diamond mark facing the key- 5 date inhibitor and corresponding to a wave- board. length in the range of 520 to 580 nm; - Cover the cell with the instrument cap. Orient the analyzing the sample to determine the presence cap’s curved surface toward the keyboard to match and the intensity of the characteristic color; and the grooves in the instrument case. providing an indication of the concentration of - Zero the instrument by pressing the ZERO key. 10 molybdate inhibitor in the lithium bromide brine

- Measure Li2MoO4 concentration in each unknown of the sample as a function of the presence and sample by inserting the unknown sample cell, cov- intensity of the characteristic color. ering the cell compartment and pressing the READ key. 2. The method of Claim 1 wherein the sample is ana- - Multiply the number displayed in the instrument re- 15 lyzed and an indication of molybdate concentration adout by 100 to obtain Li2MoO4 concentration in is provided using a spectrophotometer, and further PPM. characterized by the step of calibrating the spec- trophotometer. The Li2MoO4 concentration measured using this method is not normalized to 55 % LiBr. 20 3. The method of Claim 2 wherein the step of calibrating [0027] Tests comparing the above-described equip- the spectrophotometer is characterized by the ment and process with the more conventional, standard steps of: ICP process yield results which demonstrate the accu- racy and repeatability of the technique. The range of var- mixing the selected reagent with a reference iation between the techniques is acceptable in monitoring 25 sample of lithium bromide brine which contains the concentrations of molybdate inhibitor in the chiller a known amount of molybdate inhibitor; brines to assure that concentrations in the 100-200 ppm analyzing the reference sample to determine the range can be maintained. intensity of the characteristic color; [0028] The preferred embodiment has described the establishing the determined intensity of the use of a colorimeter 10 for determining the concentration 30 characteristic color for the reference sample as of molybdate in a sample, to obtain the accuracy, objec- a reference indication of a known concentration tivity, and repeatability of such an instrument in making of molybdate inhibitor; and colorimetric determinations. However, it will be appreci- determining the concentration of the unknown ated that other means may be used for determining mo- sample of molybdate inhibitor in the lithium bro- lybdate concentration based on the intensity of the char- 35 mide brine as a substantially linear function of acteristic color of the reacted sample. For instance, an- the indication provided by the spectrophotome- other technique which may be used for on-site analysis ter. comprises the use of a color comparator system in which the user is provided with an array of reference color in- 4. The method of Claim 3 wherein the known amount dicia or charts correlated to respective concentrations of 40 of molybdate inhibitor in the lithium bromide brine of molybdate in the reacted sample. By visually comparing the reference sample is zero. the color of the reacted sample to the reference color indicia, the user can determine the closest color match 5. The method of Claim 4 wherein the characteristic and an associated value of molybdate concentration. color of the sample containing a molybdate inhibitor This technique is inexpensive but typically less objective 45 when mixed with the reagent corresponds to a wave- and accurate than the colorimeter. length in the region near 550 nm, and the step of analyzing the sample comprises spectrophotomet- rically analyzing the sample substantially in an opti- Claims cal wavelength region near 550 nm. 50 1. A method of quantitatively analyzing molybdate in- 6. The method of Claim 5 wherein the step of spectro- hibitor present in lithium bromide brine, character- photometrically analyzing the sample containing mo- ized by the steps of: lybdate inhibitor is performed on a hand-held color- imeter. obtaining a sample of the lithium bromide brine 55 containing an unknown quantity of molybdate 7. The method of any preceding claim wherein the step inhibitor; of obtaining a sample of lithium bromide brine con- mixing a selected reagent, which is SnCl2 in HCl taining an unknown quantity of molybdate inhibitor

5 9 EP 1 058 113 B1 10

further includes the step of filtering said sample to teristischen Farbe für die Referenzprobe als ei- remove suspended particulate. ne Referenzangabe einer bekannten Konzen- tration an Molybdat-Inhibitor; und 8. The method of any preceding claim wherein the sam- Bestimmen der Konzentration der unbekannten ple is analyzed and an indication of molybdate con- 5 Probe an Molybdat-Inhibitor in der Lithiumbro- centration is provided by a user of a color comparator mid-Salzlösung als eine im wesentlichen lineare system, the user determining molybdate concentra- Funktion der von dem Spektralphotometer be- tion by comparing the characteristic color and inten- reitgestellten Angabe. sity of the sample with color references correlated with and indicating differing molybdate concentra- 10 4. Verfahren nach Anspruch 3, bei dem die bekannte tions. Menge an Molybdat-Inhibitor in der Lithiumbromid- Salzlösung der Referenzprobe Null ist.

Patentansprüche 5. Verfahren nach Anspruch 4, bei dem die charakte- 15 ristische Farbe der einen Molybdat-Inhibitor enthal- 1. Verfahren zum quantitativ Analysieren eines in einer tenden Probe, wenn sie mit dem Reagenz gemischt Lithiumbromid-Salzlösung vorhandenen Molybdat- ist, einer Wellenlänge in dem Bereich nahe 550 nm Inhibitors, gekennzeichnet durch folgende Schrit- entspricht, und der Schritt des Analysierens der Pro- te: be ein spektralphotometrisch Analysieren der Probe 20 im wesentlichen in einem optischen Wellenlängen- Beschaffen einer Probe der Lithiumbromid- bereich nahe 550 nm aufweist. Salzlösung, die eine unbekannte Menge an Mo- lybdat-Inhibitor enthält; 6. Verfahren nach Anspruch 5, bei dem der Schritt des Mischen eines ausgewählten Reagenz, das spektralphotometrisch Analysierens der Molybdat- 25 SnCl2 in HCl (aq) ist, mit einer Probe, um bei Inhibitor enthaltenden Probe mit einem tragbaren Anwesenheit von Molybdat-Inhibitor eine cha- Kolorimeter durchgeführt wird. rakteristische Farbe der Probe zu erzeugen, wo- bei die Intensität der charakteristischen Farbe 7. Verfahren nach irgendeinem vorangehenden An- eine Funktion der Konzentration des Molybdat- spruch, bei dem der Schritt des Beschaffens einer Inhibitors ist und einer Wellenlänge in dem Be- 30 Probe einer Lithiumbromid-Salzlösung, die eine un- reich von 520 bis 580 nm entspricht; bekannte Menge an Molybdat-Inhibitor enthält, au- Analysieren der Probe, um das Vorhandensein ßerdem den Schritt des Filtrierens der Probe, um und die Intensität der charakteristischen Farbe suspendiertes Teilchenmaterial zu entfernen, um- zu bestimmen; und fasst. Schaffen einer Konzentrationsangabe des Mo- 35 lybdat-Inhibitors in der Lithiumbromid-Salzlö- 8. Verfahren nach irgendeinem vorangehenden An- sung der Probe als eine Funktion des Vorhan- spruch, bei dem die Probe analysiert wird und eine denseins und der Intensität der charakteristi- Molybdat-Konzentrationsangabe von einem Benut- schen Farbe. zer eines Farbvergleichersystems bereitgestellt 40 wird, wobei der Benutzer die Molybdatkonzentration 2. Verfahren nach Anspruch 1, bei dem die Probe ana- durch Vergleichen der charakteristischen Farbe und lysiert wird und eine Molybdat-Konzentrationsanga- Intensität der Probe mit Farbreferenzen, die mit un- be unter Verwendung eines Spektralphotometers terschiedlichen Molybdatkonzentrationen korreliert geschaffen wird, und das außerdem durch den sind und unterschiedliche Molybdatkonzentrationen Schritt des Kalibrierens des Spektralphotometers 45 anzeigen, bestimmt. gekennzeichnet ist.

3. Verfahren nach Anspruch 2, bei dem der Schritt des Revendications Kalibrierens des Spektralphotometers gekenn- zeichnet ist durch folgende Schritte: 50 1. Procédé d’analyse quantitative d’inhibiteur de moly- bdate présent dans de la saumure de bromure de Mischen des ausgewählten Reagenz mit einer lithium, caractérisé par les étapes consistant à : Referenzprobe einer Lithiumbromid-Salzlö- sung, die eine bekannte Menge an Molybdat- obtenir un échantillon de la saumure de bromure Inhibitor enthält; 55 de lithium contenant une quantité inconnue d’in- Analysieren der Referenzprobe, um die Intensi- hibiteur de molybdate ; tät der charakteristischen Farbe zu bestimmen; mélanger un réactif choisi, qui est le SnCl2 dans Festlegen der bestimmten Intensität der charak- du HCl (aq), avec un échantillon pour créer une

6 11 EP 1 058 113 B1 12

couleur caractéristique de l’échantillon en pré- 7. Procédé selon l’une quelconque des revendications sence de l’inhibiteur de molybdate, l’intensité de précédentes, dans lequel l’étape d’obtention d’un la couleur caractéristique étant fonction de la échantillon de saumure de bromure de lithium con- concentration de l’inhibiteur de molybdate et tenant une quantité inconnue d’inhibiteur de molyb- correspondant à une longueur d’onde dans la 5 date comprend en outre l’étape de filtration dudit plage de 520 à 580 nm ; échantillon pour éliminer la matière particulaire en analyser l’échantillon pour déterminer la présen- suspension. ce et l’intensité de la couleur caractéristique ; et procurer une indication de la concentration de 8. Procédé selon l’une quelconque des revendications l’inhibiteur de molybdate dans la saumure de 10 précédentes, dans lequel l’échantillon est analysé bromure de lithium de l’échantillon en tant que et une indication de la concentration en molybdate fonction de la présence et de l’intensité de la est procurée par un utilisateur d’un système compa- couleur caractéristique. rateur de couleur, l’utilisateur déterminant la concen- tration en molybdate en comparant la couleur carac- 2. Procédé selon la revendication 1, dans lequel 15 téristique et l’intensité de l’échantillon avec des ré- l’échantillon est analysé et une indication de la con- férences de couleur en corrélation avec et indiquant centration en molybdate est procurée en utilisant un des concentrations de molybdate différentes. spectrophotomètre, et en outre caractérisé par l’étape d’étalonnage du spectrophotomètre. 20 3. Procédé selon la revendication 2, dans lequel l’étape d’étalonnage du spectrophotomètre est caractérisé par les étapes consistant à :

mélanger le réactif choisi avec un échantillon de 25 référence de saumure de bromure de lithium qui contient une quantité connue d’inhibiteur de molybdate ; analyser l’échantillon de référence pour déter- miner l’intensité de la couleur caractéristique ; 30 établir l’intensité déterminée de la couleur ca- ractéristique pour l’échantillon de référence en tant qu’indication de référence d’une concentra- tion connue de l’inhibiteur de molybdate ; et déterminer la concentration de l’échantillon in- 35 connu d’inhibiteur de molybdate dans la saumu- re de bromure de lithium en tant que fonction substantiellement linéaire de l’indication procu- rée par le spectrophotomètre. 40 4. Procédé selon la revendication 3, dans lequel la quantité connue d’inhibiteur de molybdate dans la saumure de bromure de lithium de l’échantillon de référence est nulle. 45 5. Procédé selon la revendication 4, dans lequel la cou- leur caractéristique de l’échantillon contenant un in- hibiteur de molybdate, lorsqu’il est mélangé avec le réactif, correspond à une longueur d’onde dans la région proche de 550 nm, et l’étape d’analyse de 50 l’échantillon comprend l’analyse spectrophotométri- que de l’échantillon substantiellement dans une ré- gion de longueur d’onde optique proche de 550 nm.

6. Procédé selon la revendication 5, dans lequel l’étape 55 d’analyse spectrophotométrique de l’échantillon contenant un inhibiteur de molybdate est réalisée sur un colorimètre à main.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 5547660 A [0005] • US 5106581 A [0007] • JP 08105835 B [0007]

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