| 单词 | molecular weight |
| 例句 | Perhaps there is some major and as yet undiscovered atmospheric constituent—nitrogen, for example—which keeps the average molecular weight of the atmosphere high and prevents blowoff. Cosmos 1980-01-01T00:00:00Z The measurement that we use to correlate freeze point depression is a sweetener's molecular weight: The lower the molecular weight, the greater the effect of freeze point depression. The science behind the scoop: Four key factors to consider when making ice cream 2021-11-26T05:00:00Z The results confirmed that the molecular weight of the component we were interested in is 176. How Chris McCandless Died: An Update 2015-02-11T05:00:00Z Adds Dr. Cleaves: "From a chemical standpoint, the differences between biotic and abiotic samples relate to things like water solubility, molecular weights, volatility and so on." Did life exist on Mars? Other planets? With AI's help, we may know soon 2023-09-25T04:00:00Z The passive forms of transport, diffusion and osmosis, move material of small molecular weight. Concepts of Biology 2013-04-25T00:00:00Z On a recent day in C2N’s lab, scientist Samantha Koch prepared plasma samples for analysis by mass spectrometers, instruments that identify compounds by molecular weight. Is it Alzheimer’s? Families want to know, and blood tests may offer answers. 2022-11-17T05:00:00Z Since molecular weights and densities of materials were well established, knowing atomic and molecular sizes allowed a precise value for Avogadro’s number to be obtained. College Physics for AP Courses 2015-08-12T00:00:00Z Some bacteria are resistant to the antibiotic penicillin because they produce penicillinase, an enzyme with a molecular weight of 3 104 g/mol that converts penicillin into inactive molecules. Chemistry 2019-02-14T00:00:00Z Hydrogen gas is so light with a molecular weight of 1 that the excess diffused into space over time and is now absent from the atmosphere. Biology for AP Courses 2022-06-09T00:00:00Z The mole of an element is its atomic weight, while a mole of a compound is the sum of the atomic weights of its components, called the molecular weight. Anatomy and Physiology 2013-06-19T00:00:00Z Lim et al. found that apical retention of these polymers depends on their slow diffusion, which is limited by their large molecular weight and the cytoplasmic actin meshwork in which they are embedded. Developing cells remember where they came from, thanks to keratin filaments 2020-08-25T04:00:00Z “The molecular weight of the sugar intermediate in reactions is 400–500 daltons,” Wu says. Exposed: cells’ sugary secrets 2020-03-15T04:00:00Z The compounds then flow into mass spectrometers that identify them by their molecular weights. Testing for Caffeine Could Help Foil Fake Urine Scam 2019-01-09T05:00:00Z One mole is defined as the gram molecular weight of the solute. Biology for AP Courses 2022-06-09T00:00:00Z H2O is strangely sticky and viscous for a molecule with such a small molecular weight. A journey through wine, spit and oil 2018-09-04T04:00:00Z The counterfeiters will try to find an antibody of similar molecular weight so that scientists who do a quick test to verify the reagents won’t be alarmed. The secret war against counterfeit science 2017-05-09T04:00:00Z Dimers are expected to be less volatile than monomers, owing primarily to higher molecular weight, but also to additional functional groups. Ion-induced nucleation of pure biogenic particles : Nature : Nature Publishing Group 2016-05-24T04:00:00Z The radio waves will bend as they pass through Pluto’s atmosphere en route to New Horizons, revealing details of its temperature and molecular weight. Nasa's New Horizons probe in final countdown to Pluto flyby 2015-07-10T04:00:00Z The molecular weight may be 100,000 daltons or more depending on the number of monomers joined. Biology for AP Courses 2022-06-09T00:00:00Z The claim used the term “molecular weight” without specifying which of three possible methods should be used to measure it. Ruling May Clear Way for Generic Version of Multiple Sclerosis Drug 2015-06-18T04:00:00Z Kohji Mitsubayashi, at the Tokyo Medical and Dental University, and colleagues impregnated a mesh with the enzyme alcohol oxidase, which converts low molecular weight alcohols and oxygen into aldehydes and hydrogen peroxide. Wine Snobs Are Right: Glass Shape Does Affect Flavor 2015-04-14T04:00:00Z He later pioneered the development of polymer vessels that control the release of large molecular weight drugs used in the treatment of cancer and mental illness. Nanotech Pioneer Langer Wins Award by Thinking Small 2015-02-10T05:00:00Z The judge relied on expert testimony to determine that someone skilled in biochemistry would understand what the phrase “a molecular weight of 5 to 9 kilodaltons” meant. Supreme Court Hands Trial Courts More Power In Teva Patent Case 2015-01-20T05:00:00Z Lipid-soluble material with a low molecular weight can easily slip through the hydrophobic lipid core of the membrane. Biology for AP Courses 2022-06-09T00:00:00Z And after the microbes grew on the polyethylene for 60 days, the mass of the plastic films decreased by 10%, and the molecular weights of the polymer chains dropped by 13%. Pantry Pests Harbor Plastic-Chomping Bacteria 2014-12-04T05:00:00Z The Federal Circuit re-examined the evidence and concluded that Teva's patent claim based on the drug's molecular weight was too ambiguous. Supreme Court weighs generic drug dispute 2014-10-15T04:00:00Z The casing will dissolve based on the polymer you use, a process you can regulate by changing the molecular weight of the polymer. Nanotech Pioneer Langer Wins Award by Thinking Small 2015-02-10T05:00:00Z The elution fractions containing protein with the highest molecular weight were further examined by negative-stain electron microscopy, and samples containing the holotoxin complex were finally used for plunge freezing and cryo-EM. Mechanism of Tc toxin action revealed in molecular detail 2014-04-04T18:24:45.845Z There are molecular weight standard samples that can be run alongside the molecules to provide a size comparison. Biology for AP Courses 2022-06-09T00:00:00Z Light ends are volatile gases with low molecular weights, measured by carbon numbers, with a lower number signifying higher volatility and higher vapor pressure. Exclusive: TransCanada toughens pipeline pressure limits for gassy crude 2014-01-31T13:29:12Z The rover had taken in fine soil particles, heated them, and passed the gases that the heating drove off through its mass spectrometer, which can separate and identify the gases by molecular weight. The First Signs of Ancient Life on Mars? 2012-12-03T22:42:48Z Fortunately for the rebels, these wells produce a light sweet crude, low in sulfur and high in small molecular weight hydrocarbons. Rebel Oil in Syria 2012-11-25T19:50:53Z If equal masses are taken, the value of the constant R for different gases varies inversely as the molecular weight or as the density relative to hydrogen. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z Proteins have different shapes and molecular weights; some proteins are globular in shape whereas others are fibrous in nature. Biology for AP Courses 2022-06-09T00:00:00Z This is what we more concisely express by saying "the molecular weight of oxygen is 32," or "the molecular weight of ammonia is 17," etc., etc. Heroes of Science Chemists 2011-12-09T03:00:21.047Z We developed small–molecular weight compounds termed mannosides that specifically inhibit the FimH type 1 pilus lectin of UPEC, which mediates bacterial colonization, invasion, and formation of recalcitrant intracellular bacterial communities in the bladder epithelium. [Research Articles] Treatment and Prevention of Urinary Tract Infection with Orally Active FimH Inhibitors 2011-11-16T19:55:21.817Z The low molecular weight heparin will be sold by Watson under an arrangement with Amphastar. FDA Approves Watson Pharmaceuticals Generic Lovenox (Enoxaparin) 2011-09-19T22:23:50Z He should then be made to compare the relative molecular weights, deduced by physical means, with the definite proportions he has observed in chemical processes. Scientific Culture, and Other Essays Second Edition; with Additions 2011-09-17T02:00:31.747Z According to Rabuteau the toxic properties of the higher alcohols increase with their molecular weight and boiling point. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z But by vaporizing water and weighing the gas so produced, we find that water vapour is nine times heavier than hydrogen: now, 1: 9 = 2: 18, therefore the molecular weight of water gas is 18. Heroes of Science Chemists 2011-12-09T03:00:21.047Z The small–molecular weight compounds described herein promise to provide substantial benefit to women suffering from chronic and recurrent urinary tract infections. [Research Articles] Treatment and Prevention of Urinary Tract Infection with Orally Active FimH Inhibitors 2011-11-16T19:55:21.817Z Exactly those substances which are most important for life possess a very high molecular weight, and consequently very large molecules, in comparison with inorganic matter. Are the Planets Inhabited? 2011-04-24T02:00:07.733Z The relative molecular weights of hydrogen, some of the hydrocarbons, and iron, are such that tails composed of these molecules would behave just as do the actual tails observed and classified into these three types. A Text-Book of Astronomy 2011-01-05T03:00:57.347Z The most uncertain factor in the formula is the molecular weight M, since the molecule in solution may be quite different from that denoted by the chemical formula of the solid. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z But in Avogadro's law we have a far more accurate and trustworthy method for determining the molecular weights of compounds than any which Dalton was able to devise by his study of chemical combinations. Heroes of Science Chemists 2011-12-09T03:00:21.047Z Speaking generally, those colouring matters which have the simplest constitution are yellow, and as the molecular weight increases their colour passes into orange, red, violet and blue. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 8 "Dubner" to "Dyeing" 2010-12-26T03:00:17.840Z For example let us take colloidal substance whose molecular weight is 2000. The Mechanism of Life The fact that these compounds are insoluble in most of the solvents which can be used for molecular weight determinations makes it difficult to determine their actual molecular constitution. The Chemistry of Plant Life The associated groups are mostly of the normal saturated series, and of very high molecular weight. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5 "Cat" to "Celt" We now proceed to analyze and determine the molecular weights of as many gaseous compounds of oxygen as we can obtain. Heroes of Science Chemists 2011-12-09T03:00:21.047Z A. Werner determined the molecular weights of mercurous, cuprous and silver bromides, iodides and chlorides in pyridine solution, and obtained results pointing to the formula HgCl, etc. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1 "Calhoun" to "Camoens" Under similar conditions, the molecular weights of different substances have therefore the same ratio as the weights of equal volumes of their vapours. The Mechanism of Life From a study of the free elements Cannizzaro showed that an element may have more than one molecular weight; for example, the molecular weight of sulphur varied with the temperature. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Then, in the second place, we see that among the elements themselves, the unions of those having low molecular weights result in far more heat than do the unions of those having high molecular weights. Essays: Scientific, Political, & Speculative, Vol. I Simultaneously, gram molecular weight for gram molecular weight, something had to be transposed into yours. Long Ago, Far Away The molecular weight of mercurous chloride has given occasion for much discussion. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1 "Calhoun" to "Camoens" Hence if we fix arbitrarily the molecular weight of any one substance, the molecular weight of all other substances is thereby determined. The Mechanism of Life When this is done, such densities are measures of the molecular weights of the substances in question. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Those of relatively-low molecular weights—oxygen, hydrogen, potassium, sodium, &c.,—show great readiness to unite among themselves; and, indeed, many of them cannot be prevented from uniting under ordinary conditions. Essays: Scientific, Political, & Speculative, Vol. I To put the matter generally, in these colloidal and complex carbohydrates the ordinary physical criteria of molecular weight are wanting. Researches on Cellulose 1895-1900 In the case of soda soaps the colloidal character increases with the molecular weight of the fatty acids. The Handbook of Soap Manufacture Thus Bouchard has been able to determine by means of cryoscopy the mean molecular weight of the substances eliminated by the urine. The Mechanism of Life We now proceed to discuss molecular heats of compounds, that is, the product of the molecular weight into the specific heat. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Contrariwise, under ordinary conditions the substances of high molecular weights—the "noble metals"—are indifferent to other substances; and such compounds as they do form under conditions specially adjusted, are easily destroyed. Essays: Scientific, Political, & Speculative, Vol. I This, however, is a 'net' result, and leaves undetermined the degree of hydration of the recovered cellulose as of hydrolysis of the original to groups of lower molecular weights. Researches on Cellulose 1895-1900 The molecular weights of the bases, phenols and chemicals employed are the following:— 1. The Dyeing of Cotton Fabrics A Practical Handbook for the Dyer and Student The molecular weight M may be determined by dividing the original weight x by n. The Mechanism of Life The first set provides evidence as to the molecular weight of a substance: these are termed “colligative properties.” Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Accordingly it is best to adopt oxygen as the standard element with which to compare the molecular weights of other gases, being careful to keep the oxygen atom equal to 16. An Elementary Study of Chemistry Attempts have been made to determine the molecular weights of the cellulose esters in solution, by observations of depression of solidifying and boiling-points. Researches on Cellulose 1895-1900 However, since it was impossible to determine the molecular weight, he could not say what the gas was, save that the empirical formula was C62TH H39O27N5. The Black Star Passes It is equal to the molecular weight of the ion, divided by 96.537 times its valency. The Mechanism of Life In practice it is generally more convenient to determine the density, the molecular volume being then obtained by dividing the molecular weight of the substance by the density. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Determination of the molecular weights of gases from their weights compared with oxygen. An Elementary Study of Chemistry The celluloses are in condensed hydroxyl union with the lignone, but the combination occurs by complexes of relatively large molecular weight. Researches on Cellulose 1895-1900 Acids like sulphuric acid are termed bibasic, and their equivalent is only half the molecular weight. A Text-book of Assaying: For the Use of Those Connected with Mines. The molecular weight of hydrogen has been arbitrarily fixed as two, and hence the molecular weight of any substance will be double its gaseous density when compared with that of hydrogen. The Mechanism of Life In place of the relative molecular weights, attention was concentrated on relative atomic or equivalent weights. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Deduction of atomic weights from molecular weights and equivalents. An Elementary Study of Chemistry We should also conclude that the cellulose type of constitution covers a very wide range of minor variations of molecular weight or aggregation. Researches on Cellulose 1895-1900 The molecular weight, therefore, is 32 + 32 + 56—that is, 120. A Text-book of Assaying: For the Use of Those Connected with Mines. Hence it was imperative to determine without doubt the molecular weight of some two typical isomers. Scientific American Supplement, No. 643, April 28, 1888 Simultaneously with this discussion of the atom and molecule, great controversy was ranging over the constitution of compounds, more particularly over the carbon or organic Atomic and molecular weights. compounds. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" The next step is to obtain the molecular weights of a large number of compounds containing nitrogen. An Elementary Study of Chemistry The results show that, in general, the capacity of a substance to lower the freezing point of nitro-glycerine depends, not upon its freezing point, or its chemical composition or constitution, but upon its molecular weight. Nitro-Explosives: A Practical Treatise The molecular weight is the sum of the atomic weights of the group. A Text-book of Assaying: For the Use of Those Connected with Mines. In this difficulty Prof. Meyer has tested the discovery of M. Raoult upon a number of compounds of known molecular weights, and found it perfectly reliable and easy of application. Scientific American Supplement, No. 643, April 28, 1888 It may be generally inferred that an increase in molecular weight is accompanied by a change in colour in the direction of the violet. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Determine the molecular weight of a large number of compounds of the element, and by analysis the part of the molecular weight due to the element. An Elementary Study of Chemistry But the vapor density of water, referred to air, is 0.635, and this number multiplied by the constant 28.87, gives 18 as the molecular weight of water, or exactly twice that accepted by chemists. Scientific American Supplement No. 822, October 3, 1891 This is particularly true if, in connection with the normal solution, the weight of substance for analysis is chosen with reference to the atomic or molecular weight of the constituent to be determined. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes Weights.—A new and simple method of determining molecular weights for unvolatilizable substances. Scientific American Supplement, No. 643, April 28, 1888 Formulae which merely express the relative number of atoms of the different elements present in a compound are termed empirical formulae, and the formulae of all compounds whose molecular weights are undetermined are necessarily empirical. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" The molecular weight of a substance containing hydrogen and chlorine was 36.4. An Elementary Study of Chemistry The physical properties of the alcohols exhibit a gradation with the increase of molecular weight. The Project Gutenberg Encyclopedia Volume 1 of 28 By a similar course of reasoning the conclusion is reached that the normal solution of sodium thiosulphate should contain, per liter, its molecular weight in grams. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes The molecular weight was determined by saponification with alcoholic potash, and subsequent titration of the excess of potash employed. Scientific American Supplement, No. 447, July 26, 1884 Is the molecular weight not in every instance = two volumes? Scientific American Supplement, No. 286, June 25, 1881 We have now seen how the equivalent of an element and the molecular weight of compounds containing the element can be obtained. An Elementary Study of Chemistry According to the international atomic weights adopted in 1908, the molecular weight of acetylene is 26.016 if O = 16; in round numbers, as ordinarily used, it is 26. Acetylene, the Principles of Its Generation and Use A Practical Handbook on the Production, Purification, and Subsequent Treatment of Acetylene for the Development of Light, Heat, and Power This is, in reality, a very simple problem in proportion, making use of the atomic or molecular weights of the substances in question which are chemically equivalent to each other. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes It is permissible to assume that the irregularity exhibited by Neradol D as regards the analytical estimation of its tannin contents is connected with the low molecular weight of the tanning principle. Synthetic Tannins The impossibility of the correctness of the hypothesis is now revealed by the fact just demonstrated, that in the case of nitrogen the specific gravity does not coincide with the molecular weight. Scientific American Supplement, No. 286, June 25, 1881 By multiplying these densities by 28.9 the molecular weights of the compounds as given in the second column are obtained. An Elementary Study of Chemistry Taking the molecular weight of acetylene as 26, we have 26 C_p - 26 C_v = 2 cal., and C_p = 1.26 C_v. Acetylene, the Principles of Its Generation and Use A Practical Handbook on the Production, Purification, and Subsequent Treatment of Acetylene for the Development of Light, Heat, and Power To determine the quantity of the barium chloride required, it is necessary to include in its molecular weight the water of crystallization, since this is inseparable from the chloride when it is weighed. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes The determination of the elementary composition of compounds of high molecular weight is greatly facilitated by employing their halogen derivatives; so, for instance, is p iodophenyl maltosazone very suitable. Synthetic Tannins The weight of the silver salt thus produced was only .37 gr., much too small a quantity for the accurate determination of the molecular weight of the acid. Insectivorous Plants We have, then, this general procedure: Find the percentage composition of the substance and also its molecular weight. An Elementary Study of Chemistry Definition.—We have seen that the molecular weight of a compound, as well as of most elements, is obtained from the vapor density by doubling the latter. An Introduction to Chemical Science The molal solution is assumed to contain one molecular weight in grams in a liter of solution. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes When weights of substances which are proportional to their molecular weights are dissolved in the same weight of solvent, the rise of the boiling point is the same in each case. An Elementary Study of Chemistry When weights of substances which are proportional to their molecular weights are dissolved in the same weight of solvent, the lowering of the freezing point is the same in each case. An Elementary Study of Chemistry It will be well in connection with molecular weights to consider how the formula of a compound is decided upon, for the two subjects are very closely associated. An Elementary Study of Chemistry Molecular Symbols.—From the vapor density of the gases— column 2—we obtain their molecular weight— column 3. An Introduction to Chemical Science By taking advantage of these laws it is possible to determine when two solutions contain the same number of molecules of two dissolved substances, and consequently the relative molecular weights of the two substances. An Elementary Study of Chemistry The figures so obtained will be the respective parts of the molecular weight due to the several atoms. An Elementary Study of Chemistry It will be recalled that the molecular weight of a gas is determined by ascertaining the weight of 22.4 l. of the gas. An Elementary Study of Chemistry From the molecular weight calculate the weight of 1 l. of each of these gases. An Elementary Study of Chemistry This gives 2 atoms of O to the molecule, i.e. the molecular weight / the atomic weight. An Introduction to Chemical Science Solve Problem 10, Chapter XVIII, without using molecular weights. An Elementary Study of Chemistry A substance consisting of oxygen and hydrogen was found to have a molecular weight of 34. An Elementary Study of Chemistry Multiply the molecular weight successively by the percentage of each element present, to find the amount of the element in the molecular weight of the compound. An Elementary Study of Chemistry Solve Problem 18, Chapter XVII, without using molecular weights. An Elementary Study of Chemistry In case of a compound gas, half the molecular weight must be taken for the vapor density; e.g. dif. An Introduction to Chemical Science If the molecular weight of any gas is known, the weight of a liter of the gas under standard conditions may be determined by dividing its gram-molecular weight by 22.4. An Elementary Study of Chemistry From the molecular weight of the same gases calculate the density of each, referred to air as a standard. An Elementary Study of Chemistry As a summary we can then make the following statement: The molecular weight of any gas may be determined by calculating the weight of 22.4 l. of the gas, measured under standard conditions. An Elementary Study of Chemistry Determination of molecular weights from density of gases. An Elementary Study of Chemistry Its vapor density at 1,000 degrees is 32; hence its molecular weight is 64, i.e. vapor density x 2; and there are 2 atoms in its molecule at that temperature, molecular weight / atomic weight. An Introduction to Chemical Science If each of these molecular weights is multiplied in turn by the percentage of nitrogen in the compound, the product will be the weight of the nitrogen in the molecular weight of the compound. An Elementary Study of Chemistry What is the molecular weight, i.e. the weight of its molecule? An Introduction to Chemical Science To obtain the vapor density of any compound from the formula, we have only to divide its molecular weight by two. An Introduction to Chemical Science If by any other means we can get this information, we can make use of the knowledge so gained to determine the molecular weights of the two substances. An Elementary Study of Chemistry Its vapor density is 150, which gives 300 for the molecular weight, while its least combining or atomic weight is 75. An Introduction to Chemical Science Find the vapor density, and from that the molecular weight, remembering that the latter is twice the former. An Introduction to Chemical Science |
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