CS248579B1 - A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite - Google Patents
A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite Download PDFInfo
- Publication number
- CS248579B1 CS248579B1 CS395085A CS395085A CS248579B1 CS 248579 B1 CS248579 B1 CS 248579B1 CS 395085 A CS395085 A CS 395085A CS 395085 A CS395085 A CS 395085A CS 248579 B1 CS248579 B1 CS 248579B1
- Authority
- CS
- Czechoslovakia
- Prior art keywords
- mercaptobenzothiazole
- solution
- cyclohexylamine
- benzothiazole
- aqueous
- Prior art date
Links
Landscapes
- Thiazole And Isothizaole Compounds (AREA)
- Investigating Or Analysing Materials By The Use Of Chemical Reactions (AREA)
Abstract
Riešenie sa týká sposobu kontroly procesu oxidačnej kondenzáoie 2-merkaptobenztiazolu chlornanom sodným v nadbytku cyklohexylaminu za vzniku N-cyklohsxyl - -2-benztiazolylsulfonamidu spektrofotometricky. Po odfiltrovaní suspenzie oxidovanéj rsakčnsj amesi sa odpipetuje časí filtrátu, zriedi sa porovnávacím roztokom a spektrofotometricky sa stanoví koncentrácia cyklohexylamínovej soli 2-msrkaptobenztiazolu z absorbancie pri 270 - 350 nm. Ako porovnávací roztok sa použije vodný roztok benztiazolu, chloridu sodného, hydroxidu sodného alebo cyklohexylamínu s. nim. obsahom benztiazolu 1,5. 10-3M, alebo ich zmesi. ■The solution concerns the method of controlling the process of oxidative condensation of 2-mercaptobenzthiazole with sodium hypochlorite in an excess of cyclohexylamine to form N-cyclohexyl-2-benzthiazolylsulfonamide spectrophotometrically. After filtering off the suspension of the oxidized mixture, the filtrate is pipetted off, diluted with a comparative solution, and the concentration of the cyclohexylamine salt of 2-msrkaptobenzthiazole is determined spectrophotometrically from the absorbance at 270-350 nm. An aqueous solution of benzthiazole, sodium chloride, sodium hydroxide or cyclohexylamine with them is used as a comparative solution. benzthiazole content 1.5. 10-3M, or their mixtures. ■
Description
X 248 S79
Vynález sa týká sp osobu kontroljý^ IjrolesiF oxidačnej kofaden-zácie 2-merkaptobenztiazolu chloxnarionKsóflnym v nadbytku oýkl o -hexylaminu spektrofotometricky. lí-cyklohexyl-2-benztiazolylsulfénamid sa připravuje oxidač-nou kondenzáciou cyklohexylaminovéj soli 2-merkaptobenztiazoluroztokom chlornanu sodného podlá schémy
Je váeobecne známe, že pri výrob© gumárenských urýchlovačovsulfénamidového tjtpu je základný problém viest proces v oblastioptimálneho molámeho poměru základných zložiek 2-merkaptobenz-tiazolu ohlornanom sodným a to z hladiska selektívnosti reakcie,ako aj z hladiska akosti finálneho produktu. Klasické postupystanovenia tzv, „konca oxidácie” v procesoph vedených blízkoekvivalentných pomerov 2-merkaptobenztiazolu ku í cyklohexylamínusú založené na kvalitatívnyoh technických stanoveniach nadbytkuoxidačného činidla, napr, jedoškrobovým papierom, připadne na zá-klade nerozpustného podielu v benzéne („benzene insoluble test”)(Technická dokumentácia fy Uniroyal, USA). Tieto postupy nemož-no použit v případe procesu v nadbytku cyklohexylamínu.
Kontrola oxidaěného procesu meraním redox-potenciálu oxido-redukčnej sústavy nevedie k získaniu reprodukovatelných a inter-pret ovát elnýoh výsledkov.
Teraz sa zistilo, že je možné kontrolovat proces oxidačnějkondenzácie 2-merkaptobenztiazolu chiómanom sodným v nadbytkucyklohexylamínu spektrofotometricky spósobom podlá vynálezu.
Podstata vynálezu spočívá v principe kontroly procesu oxi-dačnej kondenzácie 2-merkaptobenztiazolu ohlornanom sodným v nad-bytku cyklohexylamínu pomocou stanovenia koncentrácie cyklohexyl-amínovej soli 2-merkaptobenztiazolu vo vodnej fáze oxidaČnej zme-si po spotřebovaní chlornanu dodného v oxidačnej reakcii.
Vzorka suspenzie oxidovánéj reakčněj zmesi sa přefiltrujea filtrát pozostávajúci z dvooh fáz sa nechá v rozdelovacom lie-viku rozdělit. Vrchná nevodná fáza obsahuje 36 - 40 % oyklohexy-lamínu, 1,9 - 2,2 % chloridu sodného, max. 0,84 % benztiazolu, 3»41 % oxidačnýoh smól, 47,7 - 51,1 % vody a 2,5 - 3,5 % cyklo-hexylamínovej soli 2-merkaptobenztiazolu, podlá stupňa naoxido-vania reakčnej zmesi. Spodná vodná fáza je vodný roztok s obsahom " 248 579 max. 10,2 % chloridu sodného, max. 0,073-% hydroxidu sodného,max. 0,26 % benztiazolu, max. 2 % cyklohexylaminu a 0,2-cp %cyklohexylaminovéj soli 2-merkaptobenztiazolu, podlá stupňanaoxidovania reakčnej zmesi. Z vodnej vrstvy sa odpipetuje potřebné množstvo vodnejvrstvy oxidačněj zmesi a po zriedení porovnávacím roztokom 1:100až 1:2 sa UV-spektroíetometričky voči porovnávaciemu roztokuodmeria absorbancia pri = 270 až 350 mna.
Ako porovnávací roztok možno použit buď vodný roztok chlo-ridu sodnéjio s prídavkom benztiazolu, tiež vodný roztok hydro-xidu sodného s prídavkom benztiazolu, alebo vodný roztok benz-tiazolu, připadne vodný roztok cyklohexyl aminu s prídavkom benz-tiazolu (výhodné ioh zmesi) , pričom koncentrácia benztiazolunie je menšia ako 1,5 · 10 M. Přidáním porovnávacieho roztoku sa vzorka vodnej fázy zriedia zároveň sa elimiituje vplyv benztiazolu na meranú absorbanoiupri « 270 - 350 am. Koncentrácia benztiazolu vo vodnej fázeje v rozmedzí od 0,-002 do 0,026 % v závislosti od kvality vstup-nej taveniny 2-merkaptobenztiazolu, ako nerafinovaného produktuprimárnej vysokotlakovej reakcie anilínu, sírouhlíka a síry. Eli-minácia vplyvu benztiazolu zaručuje reprodukovatelnost atanove-nia cyklohexyl aminové j soli 2-merkaptobenztiazolu vo vodnej fá-ze. Rozdiel absorbanoie zriedeného roztoku vodnej fázy oxidačnějzmesi oprotipíiporovnávaoiemu roztoku představuje absorbanciu pri-slúchajúou cyklohexyl aminové j soli 2-merkaptobenztiazolu vo vod-nej fáze oxidačněj zmesi.
Koncentrácia cyklohexylaminovéj soli 2-merkaptobenztiazolusa vypočítá na základe vztahu z*A » c · d-a ako „ _ z . Ao =· d . a kde o je hladaná koncentrácia cyklohexyl aminové j soli 2-merkapto- “ -3 benztiazolu v mol. dm , z je stupeň zriedenia, ktorého hodnota je 2 až 100, A je meraná absorbancia pri 315 mm, charakteristická pre cyklohexylamínovú sol 2-merkaptobenztiazolu,d je hrúbka použitej kyvety v cm a a je mólový absorbčný koeficient, ktorý má pre oyklohexyla-mínovú sol 2-merkaptobenztiazolu pri 290 - 320 »mhodnotu 2,8 10^ dm^ mol“^ cm“^.
Koncentrácia v % sa potom vypočítá podlá vztahu 248 S79 0[mol.dm"3] . mol .hmotnost cyklohexylamínovej-jq soli 2-merkaptobenztiazolu
Stupeň zriedenia závisí od konoentráoie oyklohexylaminovéjsoli 2-merkaptobenztiazolu vo vzorke, od hrůbky použitéj kyvetya musí byt zvolený tak, aby meraná hodnota absorbanoie bolav rozmedzí A » 0,8 - 1,2, čím je zaručená najvyščia přesnosta citlivost meranit.
Množstvo stanovenéj cyklohexylamínovej soli 2-merkaptobenz-tiazolu charakterizuje rožne stavy oxidačněj kondenzácie. Labora-tórnymi a prevádzkovými skúškami sa zistilo, že optimálny stavoxidačnej kondenzácie charakterizuje koncentrácia cyklohexylamínovejsoli 2«merkaptobenztiazolu vo vodnej vrstvě v rozmedzí 0,2 až0,3 % z množstva do reakcie vstupujúceho.
Ak je koncentrácia cyklohexylamínovej soli 2-merkaptobenz-tiazolu vo vodnej vrátve nižčia ako 0,2 % z množstva do reakcievstupujúoeho, v reakčnej zmesi převažuje oxidačně činidlo.
Ak je koncentrácia cyklohexylamínovej soli 2-merkaptobenztia-zolu vo vodnej vrstvě vyššia ako 0,3 % z množstva do reakcie vstu-pujúoeho, v oxidačnej zmesi je nedostatok oxidačnáho činidla. Výhoda analytickéj kontroly procesu oxidačnej kondenzácie 2-merkaptobenztiazolu chlomanom sodným v nadbytku cyklohexylamí-duvpgdlalVynálezu spočívá v možnosti udržat proces oxidačnej re-akcie v oblasti optimálnych pomerov 2-merkaptobenztiazolu a oxi-dačného činidla, pri použití substrátu s variabilným zložením, vy-jádřeným pomerom čistej zložky k oelkovej hmotnosti oxidovatel-ných látok.
Uvedené příklady objasňujú, ale neobmedzujú predmet vynálezu.Příklad 1
Suspenzia oxidovanéj reakčnej zmesi sa odfiltrovala oez fritu/S-3/ a kvapalné vrstvy sa ponechali rozdeliť v rozdelovacom lie-viku. Po oddělení sa z vodnej vrstvy odpipetoval 1 ml kvapalinydo odmemej banky a zriedil sa porovnávacím roztokom do objemu10 ml. VI cm kyvetách sa odmerala absorbancia pri7.» 290 nmproti porovnává©iemu roztoku a vypočítalo sa množstvo cyklohexy-lamínovej soli 2-merkaptobenztiazolu přítomné vo vodnej vrstvě. 248 579
Ako porovnávací roztok sa použil vodný roztok benztiazoluo konoentrácii 2 · 10 M. Množstvo nájdenej cyklohexylamínovejsoli 2-merkaptobenztiazolu bolo 5 · 10“^ M, t. 3. 0,25 % z množ-stva 0,2 M 2-merkaptobenztiazolu do reakcie vstupujúceho. V oxi-dačnom procese boli zachované optimálně poměry oxi dačného činid-la a látok oxidovátelných. Příklad 2
Suspenzia oxi dováné j re akčně 3 zmesi sa odfiltrovala cez fri-tu /3-3/ a kvapalné fázy sa ponechali rozdělit. Po oddělení saz vodnej vrstvy odpipetovalo 0,1 ml kvapaliny do odmemej bankya zriedil sa obsah porovnávacím roztokom do objemu 10 ml. VI cmkyvetách sa odmerala absorbaneia pri « 290 nm proti porovnávaoie-mu roztoku a vypočítalo sa množstvo cyklohexylamínovej soli 2-mer-kaptobenztiazolu přítomné vo vodnej vrstvě. Ako porovnávací roz-tok sa použil vodný roztok o zložení 10 % chloridu sodného, 1 % hydroxidu sodného a 0, 03 % benztiazolu. Množstvo nájdenej cyklo- «*3 hexylamínovej soli 2-merkaptobenztiazolu bolo 3,5 · 10 M, t. j.1,75 % z množstva 0,2 M 2-merkaptobenztiazolu do reakcie vstupu-júoeho. Aby boli dodržané optimálně poměry oxidačného činidlaa látok oxidovátelných, třeba do procesu oxidáoie přidat naviao8 % chlornanu sodného. Příklad 3
Suspenzia oxidovánéj reakonej zmesi sa odfiltrovala a kvapal-né vrstvy sa ponechali rozdělit v rozdelovacora lieviku. Zo spod-nej vodnej vrstvy sa odpipetovali 4 ml do odmemej banky a dopl-nil sa obsah porovnávacím roztokom do objemu 10 ml. V 0,5 cm ky-vetách sa odmerala absorbaneia pri = 315 nm proti porovnáva-ciemu roztoku a vypočítala sa koncentrácia cyklohexylaminovéj so-li 2-merkaptobenztiazolu.
Ako porovnávací roztok sa použil vodný roztok o zložení 2 %cyklohexylaminu a 0,02 % benztiazolu. Vodná vrstva obsahovala 0,12 %z 2-merkaptobenztiazolu vstupujúceho do reakcie.
Aby boli dodržané optimálně poměry oxidačného činidla a lá-tok oxi dovát el’ných, je potřebné do reakánej zmesi přidávat o 5 %chlornanu sodného menej.
X 248 S79
BACKGROUND OF THE INVENTION The present invention relates to a control of the oxidative cofadenation of 2-mercaptobenzothiazole by chloxnarion of the phosphorus in excess of hexylamine by spectrophotometry. 1-Cyclohexyl-2-benzthiazolylsulfenamide is prepared by oxidative condensation of the cyclohexylamine salt of 2-mercaptobenzothiazolurosodium salt according to the scheme.
It is generally known that in the manufacture of rubber accelerator sulfenamide, the basic problem is to process the region in the optimum molar ratio of the basic components of the 2-mercaptobenzothiazole with sodium hypochlorite in terms of both the selectivity of the reaction and the quality of the final product. Conventional procedures for the so-called "end oxidation" in the process of conducting near-equivalent ratios of 2-mercaptobenzothiazole to cyclohexylamine based on qualitative technical determinations of excess oxidizing agent, e.g., single starch paper, are due to the insoluble fraction in benzene ("benzene insoluble test"). documentation by Uniroyal, USA). These processes cannot be used in the case of a process in excess of cyclohexylamine.
Control of the oxidized process by measuring the redox potential of the oxido-reduction system does not result in obtaining reproducible and cross-reactive results.
It has now been found that it is possible to control the process of the oxidation condensation of 2-mercaptobenzothiazole with sodium chlorate in excess cyclohexylamine by the spectrophotometric method of the invention.
The principle of the invention is based on the principle of controlling the process of oxidative condensation of 2-mercaptobenzothiazole with sodium borohydride in a cyclohexylamine supernatant by determining the concentration of cyclohexyl-amine salt of 2-mercaptobenzothiazole in the aqueous phase of the oxidizing mixture after consumption of the hypochlorite supplied in the oxidation reaction.
The sample of the oxidized reaction mixture slurry is filtered and the filtrate consisting of the two-phase phase is allowed to separate in the separation liquor. The top non-aqueous phase contains 36-40% cyclohexylamine, 1.9-2.2% sodium chloride, max. 0.84% benzothiazole, 3 41% oxidation pitch, 47.7-51.1% water and 2, 5 - 3.5% of the 2-mercaptobenzothiazole cyclohexylamine salt according to the degree of oxidation of the reaction mixture. The lower aqueous phase is an aqueous solution containing "248 579 max. 10.2% sodium chloride, max. 0.073% sodium hydroxide, max. 0.26% benzothiazole, max. 2% cyclohexylamine and 0.2-cp% cyclohexylamine salt. From the aqueous layer, the necessary amount of water layer of the oxidation mixture is pipetted and, after dilution with the reference solution 1: 100 to 1: 2, the absorbance at = 270 to 350 nm is measured against the reference solution.
As a reference solution, either an aqueous solution of sodium hypochlorite with the addition of benzothiazole, an aqueous solution of sodium hydroxide with the addition of benzothiazole, or an aqueous solution of benzothiazole, or an aqueous solution of cyclohexyl amine with the addition of benzothiazole (preferred mixtures) may be used. wherein the benzothiazolunium concentration is less than 1.5 · 10 M. By adding a reference solution, the aqueous phase sample is diluted at the same time to eliminate the effect of benzothiazole on the measured absorbance of 270-350 am. The concentration of benzothiazole in the aqueous phase ranges from 0.0000 to 0.026%, depending on the quality of the 2-mercaptobenzothiazole melt, as the unrefined product-primary high-pressure reaction of aniline, carbon disulphide and sulfur. The elimination of the effect of benzothiazole guarantees the reproducibility of the cyclohexyl amine salt of 2-mercaptobenzothiazole in the aqueous phase. The difference in absorbance of the dilute aqueous phase solution of the oxidation mixture of the equilibrium solution represents the absorbance of the cyclohexyl amine salt of 2-mercaptobenzothiazole in the aqueous phase of the oxidation mixture.
The concentration of the cyclohexylamine salt of 2-mercaptobenzothiazole is calculated based on the relationship from »» c · da to z z. Ao = d. and wherein o is the fasted concentration of cyclohexyl amine salt of 2-mercapto-3-benzothiazole in mol. dm, z is the dilution degree of 2 to 100, A is the absorbance at 315 mm, characteristic of the cyclohexylamine salt of 2-mercaptobenzothiazole, d is the thickness of the cuvette used in cm and a is the mole absorption coefficient which has for the cyclohexylamine salt 2-mercaptobenzothiazole at 290-320? 2.8?
The concentration in% is then calculated according to the formula 248 S79 0 [mol.dm < 3 >] .mol% by weight of cyclohexylamine-q salt of 2-mercaptobenzothiazole
The degree of dilution depends on the concentration of the cyclohexylamine salt of the 2-mercaptobenzothiazole in the sample, and must be selected from the ridge of the cuvette used so that the measured absorbance of the helices ranges from A to 0.8 to 1.2, thus guaranteeing the highest accuracy and sensitivity of the meranites.
The amount of the determined 2-mercaptobenzothiazole cyclohexylamine salt characterizes the spicy oxidative condensation states. It has been found by laboratory and operational tests that the optimal state-oxidative condensation is characterized by the concentration of cyclohexylamine salt of 2-mercaptobenzothiazole in the aqueous layer in the range of 0.2-0.3% of the amount to be reacted.
If the concentration of the cyclohexylamine salt of the 2-mercaptobenzothiazole in the aqueous return is less than 0.2% of the amount entering the reaction, the reagent mixture is predominantly oxidized.
If the concentration of cyclohexylamine salt of 2-mercaptobenzothiazole in the aqueous layer is greater than 0.3% of the amount to be introduced into the feed, there is a lack of oxidizing agent in the oxidation mixture. The advantage of analytical control of the process of oxidative condensation of 2-mercaptobenzothiazole by sodium hypochlorite in excess of cyclohexylamide in the present invention lies in the possibility of maintaining the oxidation reaction process in the region of optimal 2-mercaptobenzothiazole and oxidizing agent ratios, using a variable composition substrate with a net purity ratio. components to the weight of oxidizable substances.
These examples illustrate, but do not limit, the subject matter of the invention
The suspension of the oxidized reaction mixture was filtered off with frit (S-3) and the liquid layers were allowed to separate in a separating drug. After separation, 1 ml of the liquid was removed from the aqueous layer into a rinsed flask and diluted to 10 ml with reference solution. The VI cm cuvettes were measured for absorbance at .790 nm compared to the solution and the amount of cyclohexylamine salt of 2-mercaptobenzothiazole present in the aqueous layer was calculated. 248 579
The reference solution used was an aqueous solution of benzothiazole with a concentration of 2 · 10 M. The amount of cyclohexylamine salt of 2-mercaptobenzothiazole found was 5 · 10 < - > M, t, 3. 0.25% of the amount of 0.2 M 2-mercaptobenzothiazole in the incoming reaction. . In the oxidation process, the ratios of oxidizing agent and oxidizing agents were optimally maintained. Example 2
The suspension of oxidized 3-mixture was filtered through a pad (3-3) and the liquid phases were allowed to separate. After separating the aqueous layer, pipette 0.1 ml of the liquid into a rinsed flask and dilute to 10 ml with the reference solution. The absorbance at < 290 nm against the comparative solution was measured in the VI cmcultures and the amount of cyclohexylamine salt of the 2-mercaptobenzothiazole present in the aqueous layer was calculated. An aqueous solution of 10% sodium chloride, 1% sodium hydroxide and 0.03% benzothiazole was used as the reference solution. The amount of cyclohexane hexylamine salt of 2-mercaptobenzothiazole found was 3.5 µM, ie 1.75% of the amount of 0.2 M 2-mercaptobenzothiazole in the inlet reaction. Sodium hypochlorite should be added to the oxidation process in order to optimally maintain the oxidizing agent / oxidizing agent ratios. Example 3
The slurry of oxidized reacon mixture was filtered off and the liquid layers were allowed to separate into a funnel divider. From the bottom aqueous layer, pipette 4 ml into a rinsed flask and make up to 10 ml with the reference solution. Absorbance at = 315 nm was measured in 0.5 cm centimeters against the reference solution and the concentration of cyclohexylamine salt of 2-mercaptobenzothiazole was calculated.
As a reference solution, an aqueous solution of 2% cyclohexylamine and 0.02% benzothiazole was used. The aqueous layer contained 0.12% of 2-mercaptobenzothiazole entering the reaction.
In order to maintain the optimum ratios of oxidizing agent and oxime emitted, it is necessary to add less 5% sodium hypochlorite to the reaction mixture.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CS395085A CS248579B1 (en) | 1985-06-03 | 1985-06-03 | A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CS395085A CS248579B1 (en) | 1985-06-03 | 1985-06-03 | A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CS248579B1 true CS248579B1 (en) | 1987-02-12 |
Family
ID=5381065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CS395085A CS248579B1 (en) | 1985-06-03 | 1985-06-03 | A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite |
Country Status (1)
| Country | Link |
|---|---|
| CS (1) | CS248579B1 (en) |
-
1985
- 1985-06-03 CS CS395085A patent/CS248579B1/en unknown
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Marsh | The estimation of inorganic phosphate in the presence of adenosine triphosphate | |
| Thannhauser et al. | Analysis for disulfide bonds in peptides and proteins | |
| US3668076A (en) | Diagnostic agent | |
| US3964870A (en) | Diagnostic composition for the determination of glucose | |
| US4143080A (en) | Method and reagent for the assay of hydroperoxide | |
| KR20010101130A (en) | Method for determination of hydrogen sulfide or sulfide ion and method for determination of specific substance utilizing said method | |
| US5527708A (en) | Sensitive and highly specific quantitative fluorometric assay for creatinine in biological fluids | |
| CS248579B1 (en) | A method of controlling the process of oxidizing condensation of 2-mercaptobenzothiazole with sodium hypochlorite | |
| US3649198A (en) | Diagnostic method for the determination of uric acid in blood | |
| Senn et al. | Minimization of a sodium dithionite-derived interference in nitrate reductase-methyl viologen reactions | |
| Steel | The determination of uric acid in biological materials | |
| SU1427300A1 (en) | Method of spectrophotometric analysis of molibdenum | |
| SU1298663A1 (en) | Method of determining sulfur | |
| SU1456849A1 (en) | Method of analyzing salicylic acid and methyl salicylate in aqueous solutions | |
| CS259557B1 (en) | A process for the oxidation of 2-mercaptobenzothiazole by hydrogen peroxide | |
| SU714280A1 (en) | Method of analysis of sodium carboxymethyl cellulose | |
| US3597160A (en) | Colorimetric method for determining thiols | |
| SU1097931A1 (en) | Method of determination of 4-methoxyphenylthiocarbamide,thiocarbamide and 4,4'-dimethoxyphenylthiocarbamide | |
| SU1548723A1 (en) | Method of determining 2,4,6-trinitropzenol | |
| SU1548724A1 (en) | Method of determining sulfamic acid and its salts in air | |
| SU709952A1 (en) | Method of spectorphotometric determining of scandium | |
| SU1239565A1 (en) | Method of quantitative determining of aniline in air | |
| SU1478113A1 (en) | Method for chromium analysis | |
| SU1354101A1 (en) | Method of determining aromatic nitroso compounds | |
| SU1460701A1 (en) | Method of photometric analysis of germanium |