123 phase and hence have no direct bearing on the retention time of solutes. However in gas-solid chromatography, a considerable quantity of the mobile phase may be adsorbed on the surface of the stationary adsorbent which diminishes the column's effective length and ability to retain solutes. In this respect helium has been found to be preferable to most other gases (GREENE and Roy, 1957) because it is adsorbed to the least extent. 3. Packed columns offer a considerable resistance to flow, which may create a pressure differential between inlet and outlet of sufficient magnitude to cause an unfavorable flow rate through a significant length of the column. A reduced inlet/outlet pressure ratio can be obtained by using light molecular weight gases toward which the column packing shows the greatest permeability. The flow rate of the mobile phase is normally adjusted by altering the column inlet pressure, for which purpose commercial pressure regulators of sufficient accuracy are available. Quantitative measurements of the flow rate can be made by a number of methods, including rotameters, orifice meters, soapfilm flow meters and displacement of water. The former two methods are the most con venient but the least accurate; moreover they create a back pressure and are temperature dependent whereas although the moving soap bubble is cumbersome to employ and unusable for continuous readings, it is preferred when the highest accuracy is required."

Als Bitterstoffe bezeichnet man bitter schmeckende, N- und S-freie, O-haltige Substanzen, die noch nicht in andere groBe Verbindungsklassen, wie Alkaloide, Farbstoffe, Sterine usw. , eingegliedert sind. Bis heute ist es nicht gelungen, eine Beziehung zwischen dem bitteren Geschmack und der chemischen Konstitution zu entdecken (75). Wenn auch viele Bitterstoffe Keton- oder Lactongruppierungen enthalten, so ist doch das Vorhandensein derartiger Gruppen zur Erregung der auf "bitter" ansprechenden Geschmackssinnes-zellen keine notwendige V oraussetzung. Das Vorkommen der Bitterstoffe ist nicht auf bestimmte Pflanzen- familien beschrankt, wenn sie auch in einigen besonders zahlreich ver- treten sind, wie z. B. in den Gentianaceen oder den Compositen. Ent- stehung oder eventuelle Aufgabe der Bitterstoffe in den Pflanzen sind vollig unbekannt. Lediglich bei den Gentianaceen sind bisher Versuche zur Lokalisierung des Bildungsortes durch 1. KORTE (9I) unternommen worden. Hier konnte sowohl durch Pfropfungsversuche wie auch durch Wurzelkulturen gezeigt werden, daB weder SproB noch Wurzel allein fur die Bitterstoffbildung verantwortlich ist. 1m allgemeinen sind die Bitterstoffe in allen Organen der Pflanzen zu finden (I37); bei den stets bitteren Gentianaceen sind die Samen bitterstoff-frei. 1m Verlauf der Vegetationsperiode kann es zu Schwankungen im Bitterstoffgehalt kommen, hieruber liegen aber ebenfalls nur wenige Untersuchungen vor (IOI). Es hat ferner in manchen Fallen den Anschein, als stiege mit zunehmendem Alter einer Pflanze auch die Bitterkeit an (75). Die Existenz der Bitterstoffe ist schon seit langer Zeit bekannt, bereits im 15. J a~rhundert werden sie in deutschen Krauterbuchern beschrieben (IIO).

I'm living my life one day at a time. Sitting here picturing home with a small tear in my eyes. Spending time with my brothers who will hold my life in their hands... line of duty inspired U.S. law. In the passionate defense of his adopted homeland, Private First Class Diego Rincon lost his life to the first-known suicide attack on U.S. soldiers in Operation Iraqi Freedom. spear fight to Baghdad with the Outlaw Platoon--a conviction that compels his proud immigrant family to assume not only the blessings but the extreme burdens of freedom. More than a timeless war story, this true account of devotion to the American dream pays tribute to liberty's brave defenders, and those they leave behind in the continued War on Terror. momentous in the wake of the war. the Army, Diego's father gave his blessing again, and his mother turned her head.

I'm living my life one day at a time. Sitting here picturing home with a small tear in my eyes. Spending time with my brothers who will hold my life in their hands... line of duty inspired U.S. law. In the passionate defense of his adopted homeland, Private First Class Diego Rincon lost his life to the first-known suicide attack on U.S. soldiers in Operation Iraqi Freedom. spear fight to Baghdad with the Outlaw Platoon--a conviction that compels his proud immigrant family to assume not only the blessings but the extreme burdens of freedom. More than a timeless war story, this true account of devotion to the American dream pays tribute to liberty's brave defenders, and those they leave behind in the continued War on Terror. momentous in the wake of the war. the Army, Diego's father gave his blessing again, and his mother turned her head.