Crystallization speed

Burning test. The powdered cocaine is placed on aluminum foil and held over a low flame or match. The cocaine will burn clear. A sugar cut will darken and burn a dark brown or black therefore the larger the cut, the darker the burn. Crystallized speed or methamphetamine will pop when burned. Salts do not burn and remain as residue (cuts such as procaine or quinine also burn fairly pure although it is alleged that procaine can be detected by a bubbling of the substance before it burns clear). 

OFFICIAL NAMES Methamphetamine STREET NAMES Crystal, speed, meth, chalk, ice, glass DRUG CLASSIFICATIONS Schedule II, stimulant OFFICIAL NAMES Phencyclidine (PCP)... 

On the street, methamphetamine is known by such names as meth, crystal meth, crystal, speed, crank or wire. Most of the stuff on the street shows the telltale signs of sloppy lab work yellow crystals, sticky crystals, or a tendency to soak up water from the air and melt. 

P(VDF-TrEE), PEO N,N- dimethylformamide Differences in crystallization speed (sequential crystallization) results in a P (VDF-TrFE) fibrillar structure leading to two dynamic-mechanical relaxations. SEM, AFM, FTIR, DSC, TGA, DMA (Costa et al. 2013)... 

The extrapolation to the density of the amorphous material gives a Tg of 160 K (see Fig. 19) for the completely amorphous material, which is extremely difficult to obtain, since the crystallization speed is so high. This temperature is in good agreement... 

In the early 2000s, another new thermoplastic polyimide entered the market, called SuperAurum, an in-mold crystallizable polyimide, which has an excellent HDT of 752°F (400°C) with carbon fiber filler. The enhancing crystallization speed enables a crystalline state even during... 

However, the whole procedure is anything but easy. Many factors are decisively involved, for example temperature, kind of amine applied, concentration, sometimes the degree of supersaturation, quality of seed crystals, speed of crystallization and other obstacles. Apparently, it took in certain cases years to obtain the first crystals as a prerequisite for turning an originally brown, very viscous undistillable mixture of four to eight pyrethroid-isomers into white crystals, containing about 100% more of the actual ingredient than before. Suitable solvents are very unpolar ones, such as hexane, or very polar ones, such as methanol. 

PrPJ f) where p is the atomic density. Note that in 15.4 the speed of crystal growth becomes a constant for nuclei much larger than the critical one. The expressions 15.3 and 15.4, refers to a diffusion-limited crystallization, which seems to apply to phase change materials as they show a maximum in the crystallization speed for temperatures in between and T. In a collision limited crystallization (which does not apply to phase change materials) D jX has to be replaced by the velocity of sound which is weakly dependent on temperature. The formation energy and the radius of the critical nucleus are given in turn hy AGc =... 

Fig. 15.10 Kinetic prefactor of the crystallization speed Wkin as a function of temperature (cf. 15.4) from NN simulations. The dashed line is an Arrhenius fit yielding an activation energy of0.26 0.03eV [97]...

Similar to homopolymers, the structural parameters of and MWD play a similar role for the properties of the random copolymers, while, the stereospecificity concept changes its meaning. In fact, the introduction of a comonomer into polymeric chain determines a discontinuity that deeply affects the molecule s crystallization behavior. The crystallization speed slows down, forcing lower total crystallinity and a reduction of the melting temperature related to the less perfect structure of the crystals. 

Zellnitz, S., Narygina, O., Resch, C., Schroettner, H., Urbanetz, N. A. (2015). Crystallization speed of salbutamol as a function of relative humidity and temperature. International Journal of Pharmaceutics, 489( -2), 170-176. 

---