Extraction hints

A student used 5.326 g of tea leaves in the experiment. How much caffeine is expected, assuming all the caffeine is extracted (Hint see Background.)... 

The Road to Recovery—Back-Extraction A Sample Extraction Performing an Extraction or Washing Extraction Hints... 

BENZALDEHYDE The precursor for speed. It makes up nearly 100% of bitter almond oil. Not a very popular oil with the DEA. Some hints Benzaldehyde is indispensable for the flavoring industry. It is the flavor in almond extract and synthetic benzaldehyde is used in all cherry flavorings. Also, there is currently a little loophole in the system when it comes to a product called Roasted Cassia Oil . Apparently, some manufacturers take cassia oil and run it through some sort of industrial process to change it into benzaldehyde. No one wanted to tell Strike the particulars of how this was done. But one company chemist gave me some hints (You can get really chatty with some of these guys). 

What is the danger associated with extracting basic soils with acid (Hint something is rapidly released.)... 

Taxol has had a most unusual clinical development history. As with many natural products that have been discovered to provide therapeutic benefit to humans, it was the extract of a plant that provided the first hint of the oncological potential of this product. Natural product chemists typically subject purified plant extracts to screening for therapeuhc achvity. In 1963, an extract of the bark of the Pacific yew tree (Taxus brevifolia (Figure 7.2) showed anti-tumor activity. This early work was done by Monroe Wall and Monsukh Wani of the Research Triangle Institute (RTI) under the auspices of the National Cancer Institute (NCI) [3]. 

Hint Use the multiple display option and display each of the NOE (ROE) difference spectra together with the ID TOCSY spectra of the individual monomer units to recognize and assign intra- and inter-residue NOEs (ROEs) respectively. Use different colours to differentiate between the spin systems of the individual monomers and use a special colour to mark NOEs among different monomers on your hardcopy. Cross check your findings with the conclusions extracted from previous data and carefully check the consistency of your H assignments in all the spectra. 

More recent studies show some variations to the above generalities. 13C and 23Na NMR studies indicate that for Na+ the complexation sequence is 18-crown-6 > 15-crown-5 > benzo-lS-crown-5,482 hinting at the need for ligand flexibility conduction data reveal that for 18-crown-6 the stability sequence is K+>Rb+>Cs+>Na+ 483 extraction studies using metal picrates show that for benzo-15-crown-5, Na+ > K+ > Rb+ > Li+ > Cs+ for 1 1 complexes and that for the corresponding 1 2 complexes K+ > Rb+ > Cs+ 484 further extraction work indicated... 

Now you wonder how much ethyl acetate you should use. Calculate the volume of ethyl acetate that you need at minimum if you want to extract at least 99% of the total 1-naphthol present in the water sample. Are you happy with this preconcentration step Somebody tells you that it would be much wiser to extract the sample twice with the goal to get each time 90% of the total compound out of the water (which would also amount to 99%), and then pool the two extracts. How much total ethyl acetate would you need in this case Finally, another colleague suggests to add 3.56 g NaCl to the 20 mL sample in order to improve the extraction efficiency. How much less ethyl acetate would be required in the presence of the salt (Hint Consult Table 5.7.) Is there any other effect that the addition of NaCl would have on the extraction, and is this effect favorable for the analytical procedure chosen ... 

Conversely, neutral extracting agents possessing nitrogen electron-donor atoms in their structure (soft bases) will easily discriminate between An(III) and Ln(III) even from nitric acid feeds, thanks to covalently hinted An(III)-N interactions, the best example being the terdentate bis-triazinyl-pyridines (BTPs) or the tetradentate bis-triazinyl-bis-pyridines (BTBP). 

The first hints that the energy dependence of a + near E was different for positrons and electrons came from the results of Fromme et al. (1986, 1988) for helium and molecular hydrogen, which revealed that energy dependence than <7+(e ) and that the former falls below the latter very close to E. This type of behaviour is consistent with the expected Wannier laws for the two projectiles, though the energy width of the positron beam and other instrumental effects (see section 4.3 for a discussion of the operation of the ion extractor in this experiment) meant that the measurements were insufficiently precise for a value of the exponent to be extracted. 

By applying methods of sequential leaching, direct chemical information can be obtained and a rough assessment of the remobilization potential of the sedimented heavy metals is possible. Because of the lack of specifity of the extraction procedures particular species cannot be identified (see also critical hints in [KHEBOIAN and BAUER,... 

---