r)l() STATE BOARD OP AGRICULTURE. 



especially siuce it did not seem advisable to employ acid and alkaline 

 solutions of potassium permanganate for punfying the gases. Accord- 

 ingly, after various preliminary experiments, an apparatus represented 

 by Fig. 1, was arranged for enclosing insects in a current of pure 

 hydrogen (i. e., hydrogen free from oxygen and carbon dioxide). The 

 manixjulation of this apparatus to obtain hydrogen known to be free 

 from oxygen and carbon dioxide, and the method of carrying out the 

 experiment may be described briefly. Referring to Fig. 1, hydrogen was 

 generated in "A" by the inter-action of sulphuric acid and pure lunij) 

 zinc. "B" contained potassium hydroxide. "C" represents a copper 

 tube which was packed full of copper dust for the absorption of oxygen. 

 The middle of this tube was kept hot by a flame. Over the connection's 

 at either end of the tube, cooling pads, on which cold water could 

 drip, were placed. "D," '*F" and ''H," at the beginning of the experi- 

 ment, contained potassium hydroxide solution made up at the rate 

 of 120 grams of potassium hydrate in 80 c. c. of water; ''E" and "G" 

 contained pyrogalic acid in water — rate, 5 grams in 15 c. c. of water. 

 "I" contained a weak solution of barium hydrate used as a final wash. 

 "J" represents a cell which consisted of two pieces of light, clear plate 

 glass between which was clamped a thick rubber gasket, having a 

 rectangular opening through the center just large enough to hold snugly 

 a specimen of Passalus cormitus. "K" was a glass tube large enough to 

 hold conveniently three specimens of the same species. The flasks "L" 

 and ''M" were arranged in place so that a measured amount of a 

 standard barium hydrate solution could be introduced at the proper 

 time. The generator was so arranged that warm sulphuric acid could 

 be introduced at any time through the long thistle-tube "T," or the 

 exhausted solution could be forced out (should that be necessary) 

 through ^'O." These operations could be performed without interfering 

 with the slow, continuous passage of hydrogen under slight pressure, 

 through the rest of the apparatus. The connecting-tubes, test-tubes 

 and flasks were all of very heavy, strong glass, rubber being used only 

 where absolutely necessary as shown. At the beginning of the experi- 

 ment, the glass connecting-tubes between "D" and "E," *'E" and "F," 

 and between "G" and "H" stood up high in the position shown by the 

 dotted line between ^'G" and "H." With every thing connected up thus, 

 gas tight, a lively stream of hydrogen was kept going through the ap- 

 paratus for six hours or more. Experience showed that it required al- 

 most that length of time to wash out practically the last trace of oxygen. 

 Then, the strong connecting tubes between "E" and ''F," and ''D" and 

 "E" were slowly forced down to the position shown. As the tubes 

 were pushed down, hydrogen pressure caused some of the pyrogallic 

 acid solution in ''E" to run over into the potash of 'T" and some 

 of the potassium hydrate of "D" to run over into the pyrogallic acid 

 of "E." Potassium pyrogallate which is a great absorbent of oxygen, 

 was thus formed in an atmosphere of almost pure hydrogen, and after 

 that any trace of oxygen escaping with the hydrogen through *'C" was 

 caught in the pyrogallate solutions of ^'E" and ''F." Later the con- 

 nection between "G" and "H" was forced down and so potassium 

 pyrogallate was also formed in "H." In all these operations, care was 

 taken that the solutions did not touch the rubber stoppers. The solu- 

 tion in "H" served for a test by which one might know that the hydro- 

 gen was free from all oxygen. Potassium pyrogallate, upon absorbing 



