Heptane, flash-point

A2.1 Specifications for n-Heptane Flash Point Check Grade... 

A commercial solution of f-BuLi in pentane may be substituted for t-BuLi in heptane. However, the lower volatility and higher flash-point of the heptane solvent makes t-BuLi in heptane much easier and safer to handle than this alternative. 

Ignitability-flammability. A liquid that has a flash point of less than 60°C (140°F) is considered ignitable. Some examples are benzene, hexane, heptane, benzene, pentane, petroleum ether (low boiling), toluene, and xylene(s). 

Make at least five determinations of the flash point of standard n-heptane which meets the specifications set forth in Appendix A2. Average these values. If the average differs from 23 F(—4C) by more than i3F(tl.7C), adjust the height of the taper... 

Correction factor = 23— A where A = average observed flash point of n-heptane... 

One useful blend currently being employed as a very effective silicone solvent on an industrial scale is a mixture of 80 vol % hydrocarbon heptane and 20 vol % perfluoropentane, called 1.-12808 (see Table 6.7). 1.-12808 is useful for applying silicone lubricants to numerous medical devices, such as needles, IV spikes, blood filters, and catheters. This mixture shows no flash point and no explosion limits in air. The presence of the more volatile PFC, relative to the HC,... 

DIMETHYL-4-HEPTANE (108-83-8) Forms explosive mixture with air (flash point 120°F/49°C). Incompatible with strong acids, aliphatic amines, strong oxidizers. Attacks some plastics, coatings, and rubber. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

HEPTANONE or HEPTAN-2-ONE (110-43-0) Forms explosive mixture with air (flash point 102°F/38°C). Violent reaction with strong oxidizers, aldehydes, nitric acid, perchloric acid. A variety of unstable peroxides may be formed from the reaction with hydrogen peroxide. Incompatible with aliphatic amines, aldehydes, strong bases, hydrogen peroxide, nitric acid, perchloric acid. Attacks some plastics and rubber. 

Heptane is a seven-carbon alkane and has a boiling point of 98°C, a flash point of 25°F, a flammable range of 1.05 to 6.7%, and an ignition temperature of 433°F. The stracture and molecular formula is shown in Figure 5.30. 

Flash pt 125°C (275°F). Miscible with water, methanol, alcohol, acetone, and ethyl acetate. Soluble in ether (25°C) 11% w/w. Limited solubility in benzene, trichloroethylene, methylene chloride, petrol ether, and heptane. LD50 orally in rats 5.89g/kg (Smyth). Melting point mp — 18°C Boiling point bp76o 239°C bp3.o 120°C. Flash point Flash pt 125°C (275°F). Index of refraction 1.4499. 

Four important tests which are used to characterize an engine fuel are the spontaneous ignition temperature (SIT), flash point, fire point, and smoke point. These tests are standardized, and specialized fuels have specific requirements as defined by these tests. The SIT is dependent on the composition of the fuel and the conditions of the walls of the cylinder. Diesel fuels require low SIT with short delay times of the order of 1-2 ms. The SIT of heptane (CN = 60) is 330°C, whereas benzene with CN = —10 has a SIT of 420°C. 

Again, there is no hard line between what is safe and what is not, but solvents with flash point of less than -18°C are not used. A solvent with a flash point above -18°C can be used but special precautions must be taken such as grounding of all drums and reactors to prevent buildup of electrostatic electricity and excluding all other sources of ignition. All other solvents (toxic or flash point <-18°C) must be replaced. For example, chlorinated solvents (chloroform, carbon tetrachloride), which are carcinogenic, can be replaced with ethyl acetate. Solvents such as pentane (flammable) or hexane (forms electrostatic charges) are replaced with heptanes. Benzene (a carcinogen) is replaced with toluene or xylene. Diethyl ether is replaced with t-butyl methyl ether and dioxane with tetrahydrofiiran. 

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