There exist two different spin isomers of hydrogen diatomic molecules that differ by the relative spin of their nuclei. In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (12+12); in the parahydrogen form the spins are antiparallel and form a singlet with a molecular spin quantum number of 0 (1212). At standard temperature and pressure, hydrogen gas contains about 25% of the para form and 75% of the ortho form, also known as the "normal form". The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but because the ortho form is an excited state and has a higher energy than the para form, it is unstable and cannot be purified. At very low temperatures, the equilibrium state is composed almost exclusively of the para form. The liquid and gas phase thermal properties of pure parahydrogen differ significantly from those of the normal form because of differences in rotational heat capacities, as discussed more fully in spin isomers of hydrogen. The ortho/para distinction also occurs in other hydrogen-containing molecules or functional groups, such as water and methylene, but is of little significance for their thermal properties.
How many different spin isomers exist?
2

From 1792, when the Mint Act was passed, the dollar was defined as 371.25 grains (24.056 g) of silver. Many historians[who?] erroneously assume gold was standardized at a fixed rate in parity with silver; however, there is no evidence of Congress making this law. This has to do with Alexander Hamilton's suggestion to Congress of a fixed 15:1 ratio of silver to gold, respectively. The gold coins that were minted however, were not given any denomination whatsoever and traded for a market value relative to the Congressional standard of the silver dollar. 1834 saw a shift in the gold standard to 23.2 grains (1.50 g), followed by a slight adjustment to 23.22 grains (1.505 g) in 1837 (16:1 ratio).[citation needed]
How many grains of silver did the Mint Act define the dollar as?
371.25

Sir John Call argued the advantages of Norfolk Island in that it was uninhabited and that New Zealand flax grew there. In 1786 the British government included Norfolk Island as an auxiliary settlement, as proposed by John Call, in its plan for colonisation of New South Wales. The decision to settle Norfolk Island was taken due to Empress Catherine II of Russia's decision to restrict sales of hemp. Practically all the hemp and flax required by the Royal Navy for cordage and sailcloth was imported from Russia.
What woman influenced the decision by the British to settle Norfolk Island?
Empress Catherine II of Russia