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S. P. L. Sørensen. Søren Peter Lauritz Sørensen (9 January 1868 – 12 February 1939) was a Danish chemist, known for the introduction of the concept of pH, a scale for measuring acidity and alkalinity .
The pH range is commonly given as zero to 14, but a pH value can be less than 0 for very concentrated strong acids or greater than 14 for very concentrated strong bases. [2] The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. [3]
The pH was lowered by the addition of phosphoric acid and the resulting liquid was cooled. [67] Chain determined that penicillin was stable only with a pH of between 5 and 8, but the process required one lower than that. By keeping the mixture at 0 °C, he could retard the breakdown process. [68]
Beckman model 72 pH meter, 1960. 781 pH/Ion Meter pH meter by Metrohm. A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. [ 2] The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode ...
It is based on the concentration of capsaicinoids, among which capsaicinis the predominant component. [3] The scale is named after its creator, American pharmacist Wilbur Scoville, whose 1912 method is known as the Scoville organoleptictest. [3][4]The Scoville organoleptic test is a subjective assessment derived from the capsaicinoid ...
Dean Lawrence Kamen (born April 5, 1951) is an American engineer, inventor, and businessman. He is known for his invention of the Segway and iBOT, [ 2] as well as founding the non-profit organization FIRST with Woodie Flowers. [ 3][ 4] Kamen holds over 1,000 patents. [ 5]
Heinrich Rudolf Hertz ( / hɜːrts / HURTS; German: [ˈhaɪnʁɪç ˈhɛʁts]; [ 1][ 2] 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell 's equations of electromagnetism. The unit of frequency, cycle per second, was named the ...
Iron working appears to have been invented by the Hittites in about 1200 BC, beginning the Iron Age. The secret of extracting and working iron was a key factor in the success of the Philistines. [8] [13] The Iron Age refers to the advent of iron working (ferrous metallurgy). Historical developments in ferrous metallurgy can be found in a wide ...