Empirical Formula: C₂₁H₂₁O₃P
Molecular Weight: 352.3634 g/mol
XLogP3-AA: 6.6
H-Bond Donor: 0
H-Bond Acceptor: 3
EINECS: 210-639-9 
Flash Point: 253 °C
Enthalpy of Vaporization: 64.1 kJ/mol
Boiling Point: 414 °C at 760 mmHg
Vapour Pressure: 1.1E-06 mmHg at 25 °C
Appearance: Clear fatitly yellow to yellow-green liquid
Structure of Tri-p-tolyl phosphite (CAS NO.620-42-8):
                      
IUPAC Name: Tris(4-methylphenyl) phosphite
Canonical SMILES: CC1=CC=C(C=C1)OP(OC2=CC=C(C=C2)C)OC3=CC=C(C=C3)C
InChI: InChI=1S/C21H21O3P/c1-16-4-10-19(11-5-16)22-25(23-20-12-6-17(2)7-13-20)24-21-14-8-18(3)9-15-21/h4-15H,1-3H3
InChIKey: FEVFLQDDNUQKRY-UHFFFAOYSA-N

Reported in EPA TSCA Inventory.

Poison by subcutaneous route. When heated to decomposition it emits toxic fumes of PO_x. See also ESTERS.
Hazard Codes: C
Risk Statements: 34 
R34:Causes burns.
Safety Statements: 45-36/37/39-25 
S25:Avoid contact with eyes. 
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection. 
S45:In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)

 Tri-p-tolyl phosphite , its cas register number is 620-42-8. It also can be called Tris(4-methylphenyl) phosphite ; Phosphorous acid, tris(4-methylphenyl) ester ; and Phosphorous acid, tri-p-tolyl ester (8CI) . It is hazardous, so the first aid measures and others should be known. Such as: When on the skin: first, should flush skin with plenty of water immediately for at least 15 minutes while removing contaminated clothing. Secondly, get medical aid. Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Then get medical aid soon. While, it's inhaled: Remove from exposure and move to fresh air immediately. Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product :  Wash mouth out with water, and get medical aid immediately.
In addition, Tri-p-tolyl phosphite (CAS NO.620-42-8) could be stable under normal temperatures and pressures. It is not compatible with strong oxidizing agents. And also prevent it to broken down into hazardous decomposition products: carbon monoxide, oxides of phosphorus, carbon dioxide.