For the estimation of nitrogen in nitro-cellulose take .5 to .65 grm., and place in the decomposition flask _f_ (Fig. 45), washing in with about 25 c.c. of water by alternately opening clips D and E. The air in the flask is driven out by boiling, whilst the air is shut off by the tube _i_ dipping into the basin W, which is filled with the soda lye, and tube K is placed in the test tube R, which contains a few c.c. of water. As soon as all the air is completely driven out, clips D and E are closed, and the gas jet is taken away. (This flask must be a strong one, or it will burst.) Into test tube R, 25 c.c. of concentrated solution of protochloride of iron and 10 to 15 c.c. concentrated hydrochloric acid are poured, which are sucked up into the developing flask _f_ by opening clip E, air being carefully kept from entering. The clip E is now closed, and tube _i_ is put underneath the burette, and the development of NO gas is commenced by heating the contents of the flask _f_. When the pressure of the gas in the flask has become greater than the pressure of the atmosphere, the connecting tube begins to swell at _i_, whereupon clip D is opened, and the boiling continued with frequent shaking of the bulb, until no more nitrous gas bubbles rise up into the soda lye, the distilling over of the HCl causes a crackling noise, the clip D is closed, and E opened. The burette is again put hermetically on the indiarubber stopper in basin W, and the apparatus is left to cool until the water discharged through P shows the same temperature as the water flowing through (into the cooling jacket) Z. If the level of the soda solution in the tube X is now put on exactly the same level as that in the burette by lowering or elevating the tube X as required, the volume of NO obtained in c.c. can be read off within 1/10 c.c., and the percentage of nitrogen calculated by the usual formula. [Illustration: FIG. 45.--Decomposition Flask for Schultze-Tieman Method.] The solution of protochloride of iron is obtained by dissolving iron nails, &c., in concentrated HCl, the iron being in excess. When the development of hydrogen ceases, it is necessary to filter warm through a paper filter, and acidify filtrate with a few drops of HCl. The soda solution used has a sp. gr. of 1.210 to 1.260; equals 25 deg. to 30 deg. B. The nitro-cellulose is dried in quantities of 2 grms. at 70 deg. C. during eight to ten hours, and then three hours in an exiccator over H_{2}SO_{4}. The results obtained with this apparatus are very accurate. The reaction is founded upon that of MM. Champion and Pellet's method.