502 LUTTKE'S METHOD. [BOOK n. 



be legitimately deduced, as H. and W. suppose, from the chlorine 

 determinations in a and c (a c). On the other hand, the value (H) 

 of the free hydrochloric acid cannot be deduced as they pretend 

 (H = a &), and the same remark applies to the value of the combined 

 hydrochloric acid (c) which they state as =b c. 



4. Lutike's method 1 of determining the total quantity of Hydro- 

 chloric Acid in the Gastric Contents. 



(A) The principles on which the method is based. 



The contents of the stomach in the state of health contain, in 

 addition to hydrochloric acid, certain chlorides of the alkalies and 

 alkaline earths, to wit, sodium, potassium, calcium and magnesium 

 chlorides. Ammonium chloride, on the other hand, has hitherto 

 only been discovered in the contents of the stomach in ursemia. 



The hydrochloric acid of the gastric contents is partly in the free 

 condition and partly combined with albuminous substances. 



Luttke's process depends upon the theory, which is based on a 

 large number of experimental facts collected by Martius and himself, 

 that when the gastric juice or gastric contents are ignited (at a 

 temperature much below that at which the chlorides would volatilise) 

 the entire quantity of hydrochloric acid is evolved, i.e. not only that 

 which exists in the perfectly free condition, but also that which is in 

 combination with albuminous bodies, whilst the chlorine which is in 

 combination with bases remains in the ignited residue. By deter- 

 mining, therefore, the total quantity of chlorine contained in the 

 stomach contents and then that of the chlorine in the ignited residue, 

 and by subtracting the latter from the former, there is obtained the 

 amount of chlorine which corresponds to the total hydrochloric acid 

 of the gastric contents. It is obvious that the practicability of a 

 method based upon these considerations (assuming the original 

 supposition to be correct, viz. that the whole of the hydrochloric 

 acid existing free and in organic combination is evolved) will depend 

 upon a method being available for the very accurate estimation of 

 the total chlorine present in a complex organic mixture (such as the 

 contents of the stomach), without having to subject this to any 

 process for destroying the organic substances which it contains. 

 Such a process Liittke has found in Volhard's remarkably fine 

 method for the estimation of chlorine, which has already supplanted 

 all others in the determination of the chlorine contained in the 

 urine 2 - s 4> 5 . 



1 J. Liittke, ' Eine neue Methode zur quantitativen Bestimmung der Salzsaure im 

 Mageninhalt,' Deutsche med. Wochenschr. 1891, p. 1325, and more fully developed in 

 Martius and Liittke's Die Magensdure des Menschen, see pp. 101 114. 



2 Volhard, Ann. d. Chemie u. Pharm., Vol. cxc. p. 1. 



3 F. Falk, Ber. d. deutsch. chem. Geselhch. , Vol. vin. p. 12. 



4 C. Arnold, *Kurze Methode zur massanalytischen Bestimmung der Chloride im 

 Harn,' Zelt. f. phys. Chemie, Vol. v. (1881), p. 81. 



5 E. Salkowski, ' Ueber die Bestimmung der Chloride im Harn,' Zeitsch. f. phys. 



