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  2. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    At 10 000 ppm the solution is a deep red colour. As the concentration decreases the colour becomes orange, then a vibrant yellow, with the final 1 ppm sample a very pale yellow. In science and engineering , the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities , e.g. mole fraction or ...

  3. Total dissolved solids - Wikipedia

    en.wikipedia.org/wiki/Total_dissolved_solids

    Bottled mineral water usually contains higher TDS levels than tap water.. Total dissolved solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionized, or micro-granular (colloidal sol) suspended form.

  4. XDrawChem - Wikipedia

    en.wikipedia.org/wiki/XDrawChem

    XDrawChem is a free software program for drawing chemical structural formulas, available for Unix and macOS. It is distributed under the GNU GPL . In Microsoft Windows this program is called WinDrawChem.

  5. Petroleum benzine - Wikipedia

    en.wikipedia.org/wiki/Petroleum_benzine

    Using an animal model (Wistar-strain male rats), [6] it was reported that chronic exposure (12 h a day for 24 weeks) to hydrocarbon solvent vapors conspicuously impaired peripheral nerve function in the 500 ppm n-hexane group, slightly impaired in the 200 ppm n-hexane group and petroleum benzine II group (containing 500 ppm n-hexane), and ...

  6. Pulse-position modulation - Wikipedia

    en.wikipedia.org/wiki/Pulse-position_modulation

    Pulse-position modulation (PPM) is a form of signal modulation in which M message bits are encoded by transmitting a single pulse in one of possible required time shifts. [ 1 ] [ 2 ] This is repeated every T seconds, such that the transmitted bit rate is M / T {\displaystyle M/T} bits per second.

  7. Grain per gallon - Wikipedia

    en.wikipedia.org/wiki/Grain_per_gallon

    Water chemists measure water impurities in parts per million (ppm). For understandability, hardness ordinarily is expressed in grains of hardness per gallon of water (gpg). The two systems can be converted mathematically.

  8. Per mille - Wikipedia

    en.wikipedia.org/wiki/Per_mille

    Visualisation of 1%, 1‰, 1‱, 1 pcm and 1 ppm as fractions of the large block . Percentage point difference of 1 part in 100; Percentage (%) 1 part in 100; Basis point (bp) difference of 1 part in 10,000; Permyriad (‱) 1 part in 10,000; Per cent mille (pcm) 1 part in 100,000

  9. List of chemistry mnemonics - Wikipedia

    en.wikipedia.org/wiki/List_of_chemistry_mnemonics

    A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.