Graham's law has come to denote an important class of finely divided materials. Around the time Graham did his work, the concept of molecular weight was being established largely through the measurements of gases. Daniel Bernoulli suggested in 1738 in his book Hydrodynamica that heat increases in proportion to the velocity, and thus kinetic energy, of gas particles. Italian physicist Amedeo Avogadro also suggested in 1811 that equal volumes of different gases contain equal numbers of molecules. Thus, the relative molecular weights of two gases are equal to the ratio of weights of equal volumes of the gases. Avogadro's insight together with
Same-sex marriage in the United States Same-sex marriage in the United States Same-sex marriage in the United States expanded from one state in 2004 to all fifty states in 2015 through various state court rulings, state legislation, direct popular votes, and federal court rulings. Same-sex marriage is also referred to as gay marriage, while the political status in which the marriages of same-sex couples and the marriages of opposite-sex couples are recognized as equal by the law is referred to as marriage equality. The fifty states each have separate marriage laws, which must adhere to rulings by the Supreme Court of the United States that recognize