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  2. Petroleum ether - Wikipedia

    en.wikipedia.org/wiki/Petroleum_ether

    Inhalation overexposure causes primarily central nervous system (CNS) effects (headaches, dizziness, nausea, fatigue, and incoordination). In general, the toxicity is more pronounced with petroleum ethers containing higher concentrations of aromatic compounds. n-Hexane is known to cause axonal damage in peripheral nerves. [3]

  3. GCE Ordinary Level in Sri Lanka - Wikipedia

    en.wikipedia.org/wiki/GCE_Ordinary_Level_in_Sri...

    Candidates who receive a grade of ‘W’ are considered failed in that particular subject. To be able to pass is to at least have a ‘S’ in the mandatory 6 subjects and if you fail all of the optional subjects but pass the 6 mandatory then you can still pass but if you get a ‘W’ in any of the mandatory subjects it is a immediate fail.

  4. GCSE - Wikipedia

    en.wikipedia.org/wiki/GCSE

    Untiered papers allow any grade to be achieved. Coursework and controlled assessment tasks are always untiered. In the past mathematics qualifications offered a different set of tiers, with three. These were foundation tier at grades G, F, E, and D; intermediate tier at grades E, D, C, and B; and higher tier at grades C, B, A, and A*.

  5. Hexane - Wikipedia

    en.wikipedia.org/wiki/Hexane

    Hexane (/ ˈ h ɛ k s eɪ n /) or n-hexane is an organic compound, a straight-chain alkane with six carbon atoms and the molecular formula C 6 H 14. [ 7 ] Hexane is a colorless liquid, odorless when pure, and with a boiling point of approximately 69 °C (156 °F).

  6. List of straight-chain alkanes - Wikipedia

    en.wikipedia.org/wiki/List_of_straight-chain_alkanes

    3.486 951 955 119 47 × 10 21: C 51 H 104: n-henpentacontane: 52 8 031 081 780 535 296 591: 1.092 126 741 043 54 × 10 22: C 52 H 106: n-dopentacontane: 53 2.155 777 191 357 26 × 10 19: 3.423 721 299 907 32 × 10 22: C 53 H 108: n-tripentacontane: 54 5.791 918 087 314 84 × 10 19: 1.074 254 564 589 75 × 10 23: C 54 H 110: n-tetrapentacontane ...

  7. Analytical thermal desorption - Wikipedia

    en.wikipedia.org/wiki/Analytical_thermal_desorption

    Analytical thermal desorption, known within the analytical chemistry community simply as "thermal desorption" (TD), is a technique that concentrates volatile organic compounds (VOCs) in gas streams prior to injection into a gas chromatograph (GC). It can be used to lower the detection limits of GC methods, and can improve chromatographic ...

  8. Ethiopian General Secondary Education Certificate Examination

    en.wikipedia.org/wiki/Ethiopian_General...

    2) Ethiopian General Secondary Education Certificate (EGSEC, done after grade 10) 3) Ethiopian University Entrance Examination (EUEE) results or Ethiopian Secondary School Leaving Examination The second phase of secondary education leads to two field branch that students choose one of them: natural and social science branch.

  9. List of unsolved problems in mathematics - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Clay Mathematics Institute: 2000 Simon problems: 15 <12 [7] [8] Barry Simon: 2000 Unsolved Problems on Mathematics for the 21st Century [9] 22-Jair Minoro Abe, Shotaro Tanaka: 2001 DARPA's math challenges [10] [11] 23-DARPA: 2007 Erdős's problems [12] >927: 615: Paul Erdős: Over six decades of Erdős' career, from the 1930s to 1990s