The molecular mass is the mass of a given molecule: it is measured in daltons. Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element; the related quantity relative molecular mass, as defined by IUPAC, is the ratio of the mass of a molecule to the unified atomic mass unit and is unitless. The molecular mass and relative molecular mass are distinct from but related to the molar mass; the molar mass is defined as the mass of a given substance divided by the amount of a substance and is expressed in g/mol. The molar mass is the more appropriate figure when dealing with macroscopic quantities of a substance; the definition of molecular weight is most authoritatively synonymous with molecular mass. Many common preparatory sources use g/mol and define it as a synonym of molar mass, while more authoritative sources use Da or u and align its definition more with the molecular mass; when the molecular weight is used with the units Da or u, it is as a weighted average similar to the molar mass but with different units.

In molecular biology, the weight of macromolecules is referred to as their molecular weight and is expressed in kDa, although the numerical value is approximate and representative of an average. The terms molecular mass, molecular weight, molar mass are used interchangeably in areas of science where distinguishing between them is unhelpful. In other areas of science, the distinction is crucial; the molecular mass is more used when referring to the mass of a single or specific well-defined molecule and less than molecular weight when referring to a weighted average of a sample. Prior to the 2019 redefinition of SI base units quantities expressed in daltons were by definition numerically equivalent to otherwise identical quantities expressed in the units g/mol and were thus numerically interchangeable. After the May 20th, 2019 redefinition of units, this relationship is only nearly equivalent; the molecular mass of small to medium size molecules, measured by mass spectrometry, can be used to determine the composition of elements in the molecule.

The molecular masses of macromolecules, such as proteins, can be determined by mass spectrometry. Molecular masses are calculated from the atomic masses of each nuclide present in the molecule, while molar masses are calculated from the standard atomic weights of each element; the standard atomic weight takes into account the isotopic distribution of the element in a given sample. For example, water has a molar mass of 18.0153 g/mol, but individual water molecules have molecular masses which range between 18.010 564 6863 Da and 22.027 7364 Da. Atomic and molecular masses are reported in daltons, defined relative to the mass of the isotope 12C, which by definition is equal to 12 Da. For example, the molar mass and molecular mass of methane, whose molecular formula is CH4, are calculated as follows: The more formally defined term is "relative molecular mass". Relative atomic and molecular mass values. However, the adjective'relative' is omitted in practice as it is universally assumed that atomic and molecular masses are relative to the mass of 12C.

Additionally, the "unit" Dalton is used in common practice. The mass of 1 mol of substance is designated as molar mass. By definition, the molar mass has the units of grams per mole. In the example above the standard atomic weight of carbon is 12.011 g/mol, not 12.00 g/mol. This is because occurring carbon is a mixture of the isotopes 12C, 13C and 14C which have masses of 12 Da, 13.003355 Da, 14.003242 Da respectively. Moreover, the proportion of the isotopes varies between samples, so 12.011 g/mol is an average value across different places on earth. By contrast, there is less variation in occurring hydrogen so the standard atomic weight has less variance; the precision of the molar mass is limited by the highest variance standard atomic weight, in this example that of carbon. This uncertainty is not the same as the uncertainty in the molecular mass, which reflects variance in measurement not the natural variance in isotopic abundances across the globe. In high-resolution mass spectrometry the mass isotopomers 12C1H4 and 13C1H4 are observed as distinct molecules, with molecular masses of 16.031 Da and 17.035 Da, respectively.

The intensity of the mass-spectrometry peaks is proportional to the isotopic abundances in the molecular species. 12C 2H 1H3 can be observed with molecular mass of 17 Da. In mass spectrometry, the molecular mass of a small molecule is reported as the monoisotopic mass, that is, the mass of the molecule containing only the most common isotope of each element. Note that this differs subtly from the molecular mass in that the choice of isotopes is defined and thus is a single specific molecular mass of the many possibilities; the masses used to compute the monoisotopic molecular mass are found on a table of isotopic masses and are not found on a typical periodic table. The average molecular mass is used for larger molecules since molecules with many atoms are unlikely to be composed of the most abundant isotope of each element. A theoretical average molecular mass can be calculated using the standard atomic weights found on a typical periodic table, since there is to

The Lafayette Square Historic District is a National Historic Landmark District in Washington, D. C. encompassing a portion of the original L'Enfant Plan for the city's core. It includes the 7-acre Lafayette Square portion of President's Park, all of the buildings facing it except the White House, the buildings flanking the White House to the east and west; the district was designated a National Historic Landmark in 1970. Washington, D. C. was designated as the site for the United States capital in the 1790 Residence Act, with authority given to President George Washington to ready the capital for the government by 1800. Planned by Pierre Charles L'Enfant as part of the pleasure grounds surrounding the Executive Mansion, this square was called "President's Park", now the name of the larger National Park Service unit under which it is administered, which includes the grounds of the White House and The Ellipse; the square was separated from the White House grounds in 1804, when third President Thomas Jefferson had Pennsylvania Avenue cut through east to west.

In 1824, it was renamed in honor of the Marquis de Lafayette, the Frenchman who fought in the American Revolutionary War. Lafayette Square has been used as a racetrack, a graveyard, a zoo, a slave market, an encampment for soldiers during the War of 1812, many political protests and celebrations. Andrew Jackson Downing landscaped Lafayette Square in 1851 in the picturesque style. Lafayette Square is surrounded by buildings dating back to the early 19th century, are in a variety of styles. Due to their proximity to the nation's centers of power, many of them have significance of their own, are independently listed as National Historic Landmarks; the west side of Lafayette Square is Jackson Place. It is lined by a series of townhouses built in the mid-to-late 19th century; the two at the southern end are part of the Blair House complex for visiting dignitaries. 734 Jackson Place is known as the American Peace Society house, 736 Jackson Place was a temporary residence of 26th President Theodore Roosevelt while the White House underwent renovation in 1902.

748 Jackson Place, at the north end of the block, is called the Decatur House. Flanking the White House on the west side is the Eisenhower Executive Office Building, constructed 1871-1888, as the State and Navy Department Building, once the world's largest office building. Lafayette Square is flanked on the north by H Street. From west to east, the buildings lining the street are the U. S. Chamber of Commerce Building, the Hay–Adams Hotel, St. John's Episcopal Church, the Ashburton House, the headquarters of the United States Department of Veterans Affairs. Madison Place lines Lafayette Square to the east. Buildings facing it include the Howard T. Markey National Courts Building, the Benjamin Ogle Tayloe House, the Cutts-Madison House, the Treasury Building Annex. Flanking the White House on the east side is the Treasury Building. Two urns reside between Jackson Place and Madison Place, they each stand at 5 feet tall by 4 feet wide, are made of bronze with granite bases. The sides of the urns are decorated with classical female figures.

The urns were part of the original park plan as designed by Andrew Jackson Downing in 1852. They may have been designed by his assistant Calvert Vaux; the urns were cast in a New York foundry at the orders of George M. Robeson, Secretary of the United States Navy at the time; the urns were placed on granite bases in the center of two small flower beds to the east and west sides of the Andrew Jackson statue. In 1879, they were fitted with metal pans; the park was redesigned in 1936, the urns were moved to their current location. List of National Historic Landmarks in Washington, D. C. National Register of Historic Places listings in central Washington, D. C. Lafayette Square Historic District, NRHP'travel itinerary' listing at the National Park Service Historic American Buildings Survey No. DC-676, "Lafayette Square, District of Columbia, DC", 9 photos, 3 measured drawings, 32 data pages, 1 photo caption page HABS No. DC-810, "Lafayette Square, Jackson Place", 1 color transparency, 1 photo caption page

Whirled into Happiness is a musical comedy with music by Robert Stolz, book and lyrics by Harry Graham, adapted from Stolz's Der Tanz ins Glück, with a libretto by Robert Bodanzky and Bruno Hardt-Warden. The work, billed as a "musical farce", was presented in London in 1922; the musical was staged in London by George Edwardes Ltd, a company controlled by the financier James White after the death of its founder George Edwardes. The piece opened at the Lyric Theatre in Shaftesbury Avenue on 18 May 1922 and ran for 246 performances, closing on 16 December 1922; the production was taken on tour in the provinces, with Mai Bacon from the original cast, Derek Oldham, Winnie Melville, George Gregory and Bert Weston. The J. C. Williamson company presented a production that toured Australia in 1924–25. A revised version of the show was staged in New York in 1925, under the title Sky High, ran for 217 performances. Der Tanz ins Glück was adapted into Italian as "Dance la Fortuna" and French as "Danse vers le bonheur".

Matthew Platt – Billy Merson Horace Wiggs – Austin Melford Florence Horridge – Lily St. John Albert Horridge – Tom Walls Delphine de Lavilliere – Mai Bacon Mrs Horridge – Frances Weatherall Duke of Dulchester – Hastings Lynn Duchess of Dulchester – Gladys Hirst Lord Brancaster – Reginald Palmer Lily – Wynne Bronte Antoine – Frank Atkinson Horace Wiggs, a hairdresser's assistant, visits the Majestic music hall where, owing to a striking facial resemblance, the front of house attendant, Matthew Platt, mistakes him for the Marquess of Brancaster, an intimate friend of one of the Majestic's stars, Delphine de Lavalliere. Horace is shown into the private box reserved for Brancaster and catches the eye of Florence Horridge, having a surreptitious night out with some girl friends. Platt introduces Florence to Horace, but their tête-à-tête is interrupted by her father, Albert Horridge, a nouveau-riche hatter, he has visited the Majestic because of his strong interest in Delphine. Horridge is at first indignant to find his daughter in such a place and alone with an unknown young man, but he is won over when he is told that the young man is Lord Brancaster and heir of the Duke of Dulchester.

He invites the supposed marquess to a party that evening at the Horridges' villa in the suburb of Crouch End. Horridge invites Delphine to perform at the party, she accepts on learning that Lord Brancaster is to be present, as she feels that he has been neglecting her. At the party, all goes well until Horridge bids Platt ring the Duke to tell him that his son is engaged to Florence. Delphine has recognised that Horace is not Lord Brancaster, but refrains from exposing him; the imposture is revealed when the Duchess arrive, along with the real Lord Brancaster. Horace returns to work at the hairdressing establishment, but after a sequence of farcical comings and goings there is a happy ending with Florence and Horace united. Lonson reviews were uniformly enthusiastic: In The Play Pictorial, B. H. Findon praised "the delightful strain of melody that runs through the piece … the charming dances … the merry humours of Billy Merson and Tom Walls, the vocal accomplishment of Lily St. John and Austin Melford, the diablerie of Mai Bacon and the excellent all-round interpretation … a delightful entertainment."

In The Manchester Guardian, Ivor Brown commented that the music was in the best Viennese traditions, but "naturalisation papers have been taken out for the humour … all-British clowning." The Observer wrote, ``, it is brilliant. The chief people in the cast are good." Reviewing the touring production, Neville Cardus wrote: "The bulk of the score is sheer revue. … It is rather sad to find Mr. Derek Oldham, with his pleasant voice and tasteful manner, thrown away on fustian." Pathé newsreel film of scenes from Whirled into Happiness Sky High at the IBDB database