[Illustration: FIG. 7.--NATHAN'S NITRATOR FOR NITRO-GLYCERINE. (_a_)
Nitrating Vessel; (_b_) to Separating Vessel; (_c_) to Drowning Tank;
(_e_) Nitrating Acids enter (_f_) to the Waste Acids; (_g_) Coils for
Compressed Air; (_h_) Pipes for Cooling Water; (_i_) Glass Cylinder; (_j_)
Outlet to _k_; (_k_) leading to Prewash Tank; (_l_) Glass Dome; (_m_) Pipe
to lead off for Escape of Fumes; (_n_) Vessel; (_p_) Pipe conveying
Glycerine; (_q_) Knob to turn off Glycerine; (_r_) Compressed Air Jet;
(_s_) Thermometer.]

In operating with this apparatus the nitrating acid is introduced into the
nitrating vessel by opening the cock of the pipe _e_. The glycerine is
then run in by introducing _n_ and opening the valve at its bottom, the
contents of the vessel being agitated by air blown through the
perforations of the pipe _g_. When the glycerine is all nitrated and the
temperature has slightly fallen, the circulation of the water through the
coils _h_ and the air-stirring are stopped, and the glycerine supply
vessel _n_ is removed. The nitro-glycerine as it separates from the acids
is raised by introducing by the pipe _f_ waste acid from a previous
charge, this displacing the nitro-glycerine upwards and causing it to flow
by the outlet, _j_ and pipe _k_ to the prewash tank. When nearly all the
nitro-glycerine has been separated in this manner the acids in the
apparatus may be run off by the pipe _b_ to an after separating vessel for
further settling, thus leaving the apparatus free for another nitration,
or the nitrating vessel itself may be used as an after separating bottle
displacing the nitro-glycerine with waste acid as it rises to the top, or
skimming off in the usual manner. When the separation of the nitro-
glycerine is complete the waste acid is run off and denitrated as usual, a
portion of it being reserved for the displacement of the nitro-glycerine
in a subsequent operation.