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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 HPV test substance --

Methanesulfinic acid, hydroxy-, monosodium salt [149-44-0] -- purity is less than 

(7406M) 

99%. 

FROM: Greg Fritz, Chemist . 

Industrial Chemistry Branch 

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THRU: Tracy Williamson, Chief 

Industrial Chemistry Branch (7406M) 

TO: Mike Mattheison, Chief 

Chemical Information and Testing Branch (7405M) 

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This is in response to your request for a review of the adequacy of using the hydrated form of the 

HPV test substance -- Methanesulfinic acid, hydroxy-, monosodium salt [ 149-44-0] -- to meet 

the requirements of the 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. 

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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 from the 

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 of vacuum, and in conditions of high humidity, the hydrate typically refonns in a few 

days. 

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The sponsor of this HPV chemical noted that the proposed test substance is the hydrated of 

Methanesulfinic acid, hydroxy-, monosodium salt [ 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-, monosodium salt and 11 .5% water) . 

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(URL) httpa/www.epa .gov 

Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper 
Regarding your questions as to whether it is reasonable to test the hydrated for of the HPV 

chemical, it is reasonable . EPA has accepted data for other hydrated substances subject to 

previous test rules. In the report to the Agency Administrator for the 53Td ITC priority testing list 

revisions [69 FR 2468], for example, several tungsten compounds and their hydrates were listed . 

Regarding your next question as to whether the HPV chemical 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 of chemical compounds, it is permissible, for the reasons outlined below. 

1) The HPV chemical is stabilized with sodium carbonate to maintain alkalinity. As pH 

approaches acidic conditions, the hydroxymethanesulfinic acid destabilizes to regenerate 

formaldehyde. The addition of sodium carbonate to the formulation, therefore, is 

required for the stability of the product. 

2) The HPV chemical contains about 6% sodium hydroxymethylsulfonate . The formation 

of this substance is inevitable in the presence of oxygen in the air. This is true of most 

organic R-SH moieties: 

R-SH = > R-S(=0)H = > R-S(=0)-OH 4 4 R-S(=0)(=0)-OH 

3) Sodium sulfite is present from excess reagent used to form the HPV chemical 

(formaldehyde is the limiting reagent), and sodium sulfate 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) The melting point was measured using both Thermogravimetric Analysis (TGA) and 

Differential Scanning Calorimetry (DSC). The sample was determined to have an initial 

melting point (depression of the DSC curve) of 51 °C with weight loss and 

decomposition, most likely due to the dehydration of the sample from loss of two water 

molecules. At greater than 150 °C, substantial decomposition occurred, and at 170 °C, 

the sample showed a 25% weight reduction. The melting point was determined to be 51 

°C with decomposition. 

2) When testing melting point, 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 103 g/L and 

no further water solubility testing is needed. 

In summary, sponsor's rationale to use the hydrated form of 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 form of the HPV chemical .