The results indicate that preoperative fibrinogen concentration is a limiting factor for postoperative hemostasis during and after scoliosis surgery. Preoperative measurement of fibrinogen concentration provides more information about bleeding volume and transfusion requirements than standard screening tests.

17573. Die relative Luftfeuchtigkeit, berechnet nach der Formel (3), weicht z. T. ganz erheblich von den drei anderen Grossen ab, besonders wenn der Gesamtdruck sich dem Teildruck des Wasserdampfes nahert (fur reinen Wasserdampf hat sie naturlich keinen Sinn). Von der Benutzung dieser Grosse in Sorptionsmessungen wird daher abgeraten.4. Der relative Wasserdampfdruck, die Aktivitat des Wassers und die relative Partialdichte des Wasserdampfes konnen in Sorptionsmessungen abwechslungsweise benutzt werden, wenn ein Fehler der obengenannten Grossenordnung ausser acht gelassen werden kann. Sonst wird die ausschliessliche Benutzung des relativen Wasserdampfdruckes empfohlen.bin ich fur die vielen Anregungen wahrcnd des Entstehens dieser Arbeit zu Dank verpflichtet. Die Arbeit wurde durch einen Forschungskredit derSummary. The ESCA spectrum of protonatcd 1, S-bis-(dimethy1amino)naphthalene ("proton sponge") (I) has been recorded in the region of Nls binding energies. The results indicate that IH+ possesses an znnsymmetricul N--H. .. N hydrogen bridge.The remarkable basicity of 1, 8-his-(dimethylaminojnaphthalene (I) has been attributed to relief of steric strain upon protonation [l]. Evidence for a reduction of the severe hindrance of the N-methyl groups in (I) by rotating the -N(CH,), groups out of their optimal conjugating position has been obtained by NMR-studies [l] of I as well as by ESR-studies [a] of its radical anion. However, this distortion alone would lead to an unfavorable N-lone pair interaction, which can be rationalized on the basis of Pauli's principle [ 3 ] . Reduction of this destabilizing effect could be achieved by increasing the N -. . N distance. An X-ray cristallographic analysis of I [4] has indicated that the nitrogen atoms of the rotated -N(CH,), groups are situated -0.42 A above and below the naphthalene ring plane, which results in an N * . . N distance of -2.6 A or -0.15 k larger than that expected for a structure with parallel Car-N bonds. Clearly, protonation of I will favorably decrease the lone pair interaction,

The question of the classical or non-classical nature of aryl-substituted azonium cations as well as of the pyridazinium cation has been settled by X-ray photoelectron spectroscopy in favour of the classical structure. The relative magnitude of the observed Nls binding energies is reasonably well reproduced on the basis of the theoretically calculated charge structure of these ions. The relative magnitude of the crucial intramolecular potential terms, appearing in the theoretical treatment, is also suggested from PMR.-investigations on protonated azo-compounds. The electronic structure of these species is compared with that implied by commonly accepted classical valence structures and parallels to carbo-cations are drawn. MINDO/Z calculations of the proton affinities of azo-compounds, considering structurally different conjugate acids, also support a classical azonium cation structure. The gas phase basicity of azobenzene is predicted to be higher than that of azomethane.

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