Sublimation sensitizers

Although the lUPAC has recommended the names tetrahydroborate, tetrahydroaluminate, etc, this nomenclature is not yet ia general use. Borohydrides. The alkaU metal borohydrides are the most important complex hydrides. They are ionic, white, crystalline, high melting soHds that are sensitive to moisture but not to oxygen. Group 13 (IIIA) and transition-metal borohydrides, on the other hand, are covalendy bonded and are either Hquids or sublimable soHds. The alkaline-earth borohydrides are iatermediate between these two extremes, and display some covalent character. 

CsH5)3Ti [39333-58-9] Ti(III) Cp3 green sublimes at 125 extremely air-sensitive gives (C3H3)2Ti(CO)2 with CO under... 

Supercritical and Freeze Drying. To eliminate surface tension related drying stresses in fine pore materials such as gels, ware can be heated in an autoclave until the Hquid becomes a supercritical fluid, after which drying can be accompHshed by isothermal depressurization to remove the fluid (45,69,72) (see Supercritical fluid). In materials that are heat sensitive, the ware can be frozen and the frozen Hquid can be removed by sublimation (45,69). 

In addition to the color and the tinctorial strength, which ate very important factors for the molecular design of anthraquinone dyes, affinity for fibers, various kinds of fastness (light, wet, sublimation, nitrogen oxides (NO ) gas, washing, etc), and apphcation properties (sensitivity for dyeing temperature, pH, etc) must be considered thoroughly as well. 

Alkannin occurs in the roots of the plant as the alkah-sensitive ester of angelic acid (62). It may be extracted from the roots by using boiling light petroleum ether. Treatment of this extract with dilute sodium hydroxide gives a blue solution from which the dye is precipitated by the addition of acid. The cmde product is purified by vacuum sublimation (63). Its stmcture (11) is a hydroxylated naphthoquinone with a long, unsaturated side chain (64,65) it has the (3)-configuration. 

Orange crysts by sublimation at 250-260°/3-4mm [UV Badger and Pearce Spectrochim Acta 4 280 1950]. Also recrystd from benzene under red light because it is chemiluminescent and light sensitive. 

Freeze-drying, like all drying processes, is a method to separate liquid water from a wet solid product or from a solution or dispersion of given concentration. However, the main difference is that the liquid water is separated by solidification (i.e., the formation of ice crystals) and subsequent vacuum sublimation instead of evaporation. This allows a drying at subzero temperatures which can be advantageous in case of heat-sensitive products. There are two general applications... 

These alkoxides are liquids or sublimable solids and, unless the steric effects of the alkyl chain prevent it, apparently attain octahedral coordination of the titanium by polymerization (Fig. 21.6). The lower alkoxides are especially sensitive to moisture, hydrolysing to the dioxide. Application of these organic titanates (as they are frequently described) can therefore give a... 

Intermolecular potential functions have been fitted to various experimental data, such as second virial coefficients, viscosities, and sublimation energy. The use of data from dense systems involves the additional assumption of the additivity of pair interactions. The viscosity seems to be more sensitive to the shape of the potential than the second virial coefficient hence data from that source are particularly valuable. These questions are discussed in full by Hirschfelder, Curtiss, and Bird17 whose recommended potentials based primarily on viscosity data are given in the tables of this section. 

The kinetics of NaN3 decomposition are sensitive to both pressure and composition of the surrounding atmosphere. The influence of an inert gas in suppressing sublimation of product metal has been mentioned already. The reaction of NaN3 at 623 K was strongly inhibited [711] by NO and by H2. The possible formation of transient decomposition intermediates could not, however, be distinguished from the direct interaction of added gas and azide. 

Measurement of the very low pressures associated with many of the Pu-intermetallics requires the high sensitivity afforded by target collection. To identify the gas phase species which are in the effusates, a mass spectrometer is needed. The excellent agreement between the mass spectrometric and target collection results confirms the predominance of the Pu gaseous species in the sublimation of these intermetallics. 

Zn(CH3)2 with 83b. It can be deduced from this behaviour that 83a is probably formed as an intermediate which undergoes further reduction/methylation, due to its much higher oxidative power. This assumption has been confirmed by reacting la and Sn(CH3 )4 below 0 °C, which resulted in the formation of 83a (scheme 18). 83a has been characterized by "Tc- and H-NMR, mass spectrometry and i.r. spectroscopy. Two strong vtc=o absorptions were observed at 1002 and 948 cm-1. 83a is not sensitive to oxygen or water but is very volatile and can be sublimed at room temperature even under 1 atm of N2. 

The endothermic nitride is susceptible to explosive decomposition on friction, shock or heating above 100°C [1], Explosion is violent if initiated by a detonator [2], Sensitivity toward heat and shock increases with purity. Preparative precautions have been detailed [3], and further improvements in safety procedures and handling described [4], An improved plasma pyrolysis procedure to produce poly (sulfur nitride) films has been described [5], Light crushing of a small sample of impure material (m.p. below 160°C, supposedly of relatively low sensitivity) prior to purification by sublimation led to a violent explosion [6] and a restatement of the need [4] for adequate precautions. Explosive sensitivity tests have shown it to be more sensitive to impact and friction than is lead azide, used in detonators. Spark-sensitivity is, however, relatively low [7],... 

Cl2Ga(N3)] air sensitive, sublimes at 70-100 °C in vacuum UHV-CVD Heteroepitaxial growth on Si and sapphire substrates at 650-700 °C, 1 1 films, no need for additional N source 293... 

Molybdenum (IV) bromide is a black crystalline solid which is very sensitive to oxidation and hydrolysis it should be handled only under a dry inert atmosphere. Its solubility in bromine at 51° is ca. 3.0 g./lOOO g. of bromine, and bromine solutions were found to be nonconductors. For example, at 25° both the solvent bromine and a 0.96 X 10 3 M solution in molybdenum (IV) bromide exhibited a specific conductance of 1.3 X 10-10 ohm-1 cm.-1 At 110 to 130° in vacuo, solid molybdenum (IV) bromide decomposes quantitatively into molyb-denum(III) bromide and bromine, and because of this thermal instability it cannot be sublimed except under a bromine atmosphere. 

Like the parent Cp2Be, the beryllocenes 10, 11, and 12 are sublimable, air- and oxygen-sensitive solids. They do not react with pyridine, CO, or l,3,4,5-tetramethylimidazol-2-ylidene, but do react with CNC6H3Me2-2,6 to give half-sandwich iminoacyl products via insertion into the Be-C cr-bond, described in Section 2.02.2.3.2. 

The adducts with BC13 can be sublimed without decomposition, whereas those with BBr3 decompose in vacuo reverting to the starting materials. The adducts are extremely sensitive towards hydrolysis, the latter event leading to the free dichloromethyleneorganoamines and boric acid. 

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