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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES SUBJECT: Request for evaluation of the acceptability of certain physical-chemical property

studies to satisfy TSCA §4 test rule requirements when the HPVtest substance -- Methanesulfinic acid, hydroxy-, monosodiumsalt [149-44-0] -- purity is less than (7406M) 99% . FROM : Greg Fritz, Chemist . Industrial Chemistry Branch

,T1 THRU: Tracy Williamson, Chief

Industrial Chemistry Branch (7406M) TO : Mike Mattheison, Chief

Chemical Information and Testing Branch (7405M) t

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X determination F* This is in response to your request for a review ofthe adequacy of using the hydrated formof the HPVtest substance -- Methanesulfinic acid, hydroxy-, monosodium salt [ 149-44-0] -- to meet the requirements ofthe testing program . If so, you also requested a determination as to whether the purity of the commercial product is acceptable given the TSCA §4 testing requirements 99% purity. Finally, you requested a as to whether a less pure commercial pro t would be permissible for testing and whether the test results would satisfy certain physicalchemical endpoints (melting point, boiling point, and water solubility. matrixof

form For TSCA chemical identity purposes, hydrates are treated aynixtures of a specific chemical "" substance and water. Hydrates have a stoichiometric amount of water rigidly held in the of a crystal lattice, as opposed to hygroscopic chemicals which simply absorb moisture fromthe atmosphere. The water affects properties such as melting point, water solubility, and x-ray diffraction

. Mild heating conditions under vacuum can successfully "dehydrate" these mixtures; however, the rehydration of the purified chemical substance often begins immediately upon release ofvacuum, and in conditions ofhigh humidity, the hydrate typically refonns in a few days.



### ;Z \~~ The sponsor of this HPV chemical noted that the proposed test substance is the hydrated of Methanesulfinic acid, hydroxy-, monosodiumsalt [ 149-44-0] with a corresponding molecular formula of CH403S " Na " 2 HZO . This substance is theoretically 76.6% Methanesulfinic acid, hydroxy-, monosodium salt and 23.4%water (analytically determined to be 76.9% methanesulfinic acid, hydroxy-, monosodiumsalt and 11 .5%water) .

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.epa .gov (URL) Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled PaperRegarding your questions as to whether it is reasonable to test the hydrated for of the HPV chemical, it is reasonable. EPAhas accepted data for other hydrated substances subject to previous test rules. In the report to the AgencyAdministrator for the 53Td ITCpriority testing list revisions [69 FR 2468], for example, several tungsten compounds and their hydrates were listed. Regarding your next question as to whether the HPVchemical is pure enough to meet the protocol requirements of 99°lo purity, the sample tested was not 99% pure. Even when considering the hydrated commercial product as the tested material, it is only 88.4% pure. Regarding your questions as to whether a less pure commercial product is permissible for testing, for this class ofchemical compounds, it is permissible, for the reasons outlined below . 1) The HPVchemical is stabilized with sodium carbonate to maintain alkalinity. As pH approaches acidic conditions, the hydroxymethanesulfinic acid destabilizes to regenerate formaldehyde. The addition of sodiumcarbonate to the formulation, therefore, is required for the stability ofthe product. 2) The HPVchemical contains about 6% sodiumhydroxymethylsulfonate. The formation of this substance is inevitable in the presence of oxygen in the air. This is true ofmost organic R-SH moieties: 

### R-SH = > R-S(=0)H = > R-S(=0)-OH 4 4 R-S(=0)(=0)-OH 3) Sodiumsulfite is present fromexcess reagent used to formthe HPVchemical (formaldehyde is the limiting reagent), and sodiumsulfate is present as the air oxidized sulfite (see 2 above) ; both combined account for up to 11%of the formulated commercial product. Since the reaction must be run to completion (consuming of all formaldehyde present), there will always be excess sulfite/sulfate in the sample. The 88.4%

purity of the hydrated commercial product is therefore reasonable based on the chemistry of this substance. Regarding whether the data provided for the physical-chemical endpoints of melting point, boiling point, and water solubility are adequate for the testing requirements under TSCA §4, they are adequate. 1) Themelting point was measured using both Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) . The sample was determined to have an initial melting point (depression ofthe DSCcurve) of 51 °C with weight loss and decomposition, most likely due to the dehydration of the sample fromloss oftwowater molecules. At greater than 150 °C, substantial decomposition occurred, and at 170°C, the sample showed a 25% weight reduction. The melting pointwas determined to be 51 °C with decomposition. 2) When testing meltingpoint, since the sample was determined to melt at 51 °C with decomposition, testing for boiling point is not required, as the sponsor correctly suggests.3) The water solubility test was measured using the OECD 105 test method. In the

preliminary (range finding) experiments, the upper limit used for solubility (> 1 x 103 g/L) was exceeded. The test substance value therefore was reported as > 1 x 103g/L and no further water solubility testing is needed. In summary, sponsor's rationale to use the hydrated formof the HPV chemical -- Methanesulfinic acid, hydroxy-, monosodium salt -- to obtain certain physical-chemical properties is reasonable. The sample purity (for the hydrated form) of 88.4% with stated known impurities at fixed concentrations is acceptable for testing under TSCA §4. The test methods used to determine melting point and water solubility produced adequate results. Testing boiling point is not necessary due to the decomposition of the tested substance during melting point testing. It is important to not that it should be clear in presenting the test data, that it represents the hydrated formof the HPV chemical .