Search

Particle size and suspension density of urea suspensions were investigated by means of ultrasound, optical reflectance as well as focused‐beam reflectance measurement techniques. These techniques provide similar proven nonrealistic results regarding suspension density and crystal size. The resulting data can be explained by the presence of bubbles. The influence of air bubbles on the measurement of different particle size and suspension density monitoring techniques is demonstrated and evaluated. Floating air bubbles as well as crystal‐bubble complexes are strongly affecting the results and have to be considered under real conditions. It can be demonstrated that the negative impacts on the measured data can be decreased. Special precautions have, therefore, to be taken into account for calibrations, their validation, and during crystallization monitoring or controlling to avoid faulty measured suspension densities and particle sizes caused by bubbles.

The mean particle size and suspension density of industrial ammonium sulfate and urea crystals were measured by a single ultrasound sensor in a saturated solution at only one frequency. The information on ultrasound velocity and attenuation were combined and related to characteristic properties of the solid phase of suspensions. By model identification, a correlation between the measured signals and mean particle size as well as suspension density were evaluated and verified by additional experiments. The measurements with different particle size fractions and different suspension densities up to 40 wt‐% were carried out isothermally. The approach of coupled ultrasound velocity and attenuation provides a simple technique for inline process control on the liquid and solid state of a suspension process like solution crystallization only by a single measurement device.

Needle crystals characterized by hollowness and fast crystal growth can be readily produced via phase transformation of certain hydrates when immersing in an antisolvent. Former research indicated that the diameter of tubes produced by dehydration of the model substance sodium‐2‐keto‐L‐gulonate monohydrate in methanol can be controlled by the initial antisolvent composition. However, recent investigations using single crystals demonstrate that the outer diameter of the tubes can be decreased even further at unexpected low water contents. Furthermore, a new model based on the obtained results in this study is proposed for the currently unknown initial step (nucleation) of the growth of hollow needle crystals.

The formation of hollow crystalline needles by means of a solvent‐mediated phase transformation takes place during the dehydration of hydrate crystals in methanol into hollow needle‐shaped anhydrate crystals. Here, a special way of achieving needle growth is presented. When a saturated aqueous solution of sodium‐2‐ketogulonate is dropped into methanol, a simultaneous nucleation of monohydrate crystals and anhydrate needles takes place in the alcohol. It was proven by scanning electron microscope images that these needles are hollow. By means of the variation of the production method, it is for the first time possible to observe the needle growth in a more detailed manner, and to show that the nucleation can take place at impurities and surface roughnesses. The method helped to discuss and to deepen the understanding of the growth mechanism of the hollow crystalline needles.

Hollow crystalline glucose anhydrate needles are produced based on a technique to produce hollow crystal needles by phase transformation of solvate crystals into non‐solvates. The fascinating characteristic of the glucose anhydrate needles is the possibility of closing them by a simple drying process. This creates great potential for future applications as a container system, e.g., for pharmaceutical substances. The hollowness of the needles has already been proven, but the filling of the needles has not been investigated. Due to the lack of a direct method to demonstrate the possibility of filling the needles, two indirect methods are presented to demonstrate a successful technique to enclose substances in these needles. On the one hand, the filling is proven by fluorescence microscopy of glucose anhydrate needles with enclosed rhodamine 6G. Here it is possible to visualize the fluorescence dye by observation of the broken needles. On the other hand, the concentration of included ibuprofen is examined by the means of UV spectroscopic measurements. A significant concentration of the enclosed drug is detected following the extraction out of the needle interior.

Product design is an active area of research. However, the term product designis non‐uniformly discussed in the literature, especially in the field of industrial crystallization. There is often a distinction between product design and process design. Due to that fact there is an unclear situation which leaves room for discussions. This review should help to find a more clear position. The problem is that the interrelation of product and process design quite often is underestimated in the literature. Therefore, the interrelations are highlighted here based on four examples. The examples selected are randomly taken from the entire field of crystallization (commodities, solvates, polymorphs, batch crystallization). The principles and conclusions discussed can, however, be transferred to other non‐touched areas where product and process design are considered. It is stated that “no product design is possible without process design (control)”.

Die Grundvoraussetzung eines jeden Düngers ist neben der Wirksamkeit die Lagerstabilität. Einflussfaktoren sind dabei z. B. die Morphologie oder die Festigkeit. Aus diesem Grund werden, wie z. B. in der Pharmazie auch, Additive zur Produktverbesserung eingesetzt. Bisher wurde in der Literatur nicht über die Möglichkeit diskutiert die Hydratationskinetik und die Wasseradsorption von granulierten Düngemitteln durch Additive zu beeinflussen. Die Lagerstabilität eines Produkts ist jedoch letztendlich von diesen beiden Faktoren maßgeblich beeinflusst. In der Arbeit wird für das Stoffsystem HarnstoffAmmoniumsulfat und Aluminiumsulfathydrat als Additiv ein Weg aufgezeigt, die Lagerstabilität der Düngergranalien, durch die Beeinflussung des Aluminiumhydroxids im Dünger über die kontrollierbaren Prozessparameter wie chemische Zusammensetzung, Temperatur und Verweilzeit zu steuern.

Species-specific repetitive DNA probes are a useful tool for the molecular identification of somatic hybrids. Therefore, the distribution of three repetitive DNA elements of Solanum was investigated in Solanum wild species, Solanum breeding lines, and in more distantly related species of the genera Lycopersicon, Nicotiana, and Datura. The clone pSCH15, obtained from S. circaeifolium, represents a new 168-bp repetitive element; it shows 73–79% sequence similarity to repetitive elements of S. brevidens and Lycopersicon species. The 163-bp element in pSBH6, cloned from S. bulbocastanum, turned out to be very similar (95% sequence homology) to the Lycopersicon element pLEG15/TGRI previously regarded to be present only in species of the genus Lycopersicon and in S. lycopersicoides. Lower sequence similarity of approximately 80% was observed to repetitive elements of S. brevidens which are organized differently. The repeats exhibited different degrees of specificity: by Southern hybridization the element represented by the clone pSBH6 could be detected in almost all Solanum species investigated here but only after long exposure to X-ray film. The previously described “Solanum-specific” element represented by the clone pSA287 was also found, although in a very low copy number, in Lycopersicon esculentum. Therefore, detection of the repetitive elements pSA287 and pSBH6 in those species in which the respective repeat is less represented depends on exposure time. In contrast, the element pSCH15 is prominently present only in a small number of Solanum wild species and — to some extent — in the diploid breeding lines as revealed after long exposure. Use of these repeated elements for the identification of specific genomes in protoplast-fusion hybrids between Solanum wild species and Solanum breeding lines, or between two breeding lines, was evaluated.

Highly repeated DNA of potato (Solanum sp.) was characterized by cloning various major repeated elements of the nuclear genome. The percentage of the nuclear genome of the specific fractions and the restriction enzyme patterns were determined in order to show the distribution and organization of the respective repeats in the genome of Solanum tuberosum cultivars, dihaploid breeding lines and in wild species of Solanum. Several of the clones obtained were represented in a high copy number but showed no informative RFLP patterns. More information was gained from ‘restriction satellite’ repeats. The clone pR1T320 was found to contain satellite repeats (360 bp in length) that are proportionally present in the genome of all Solanum species at frequencies, between 0.5% and 2.6% and which are differently organized. This repeat was also found in the genera Lycopersicon, Datura and Nicotiana. With various restriction enzymes characteristic RFLP patterns were detected. A more or less genus-specific element for Solanum was the 183-bp repeat (clone pSA287; between 0.2–0.4% of the nuclear genome) that was present in the majority of the Solanum species analyzed except S. kurtzianum, S. bulbocastanum and S. pinnatisectum. In a few wild species (prominently in S. kurtzianum, S. demissum and S. acaule) a specific repeat type was detected (clone pSDT382; repeat length approximately 370 bp) that could be used to trace the wild species introduced into S. tuberosum cultivars. The repeats analyzed together with the 18S, 5.8S and 25S ribosomal DNA (1.9–5.2%, corresponding to 1800-5500 rDNA copies) comprised approximately 4–7% of the Solanum genome.