Figure 71. Sterilizing oven 491 „ 72. Autoclave sterilizer 492 „ 73. Arnold’s sterilizer 493 „ 74. Lautenschläger’s thermostat 494 „ 75. Schloesing’s apparatus for nitric acid 501 „ 76. Warington’s apparatus for nitric acid 505 „ 77. Spiegel’s apparatus for nitric acid 509 „ 78. Schulze-Tiemann’s nitric acid apparatus 511 „ 79. DeKoninck’s apparatus 514 „ 80. End of delivery-tube 514 „ 81. Schmidt’s apparatus 516 „ 82. Lunge’s nitrometer 519 „ 83. Lunge’s improved apparatus 521 „ 84. Lunge’s analytic apparatus 523 „ 85. Stoklassa’s nitric acid apparatus 535 „ 86. Variation of the sodium amalgam process 537 „ 87. McGowan’s apparatus for the iodometric estimation of 544 nitric acid „ 88. Apparatus of Gooch and Gruener 547 „ 89. Method of Chabrier 566 „ 90. Schaeffer’s nitrous acid method 568 „ 91. Retort for distilling ammonia 572 „ 92. Gooch’s apparatus for boric acid 581 „ 93. Apparatus for determining sulfur 587 PART FIRST. INTRODUCTION. =1. Definitions.=—The term soil, in its broadest sense, is used to designate that portion of the surface of the earth which has resulted from the disintegration of rocks and the decay of plants and animals, and which is suited, under proper conditions of moisture and temperature, to the growth of plants. It consists, therefore, chiefly of mineral substances, together with some products of organic life, and of certain living organisms whose activity may influence vegetable growth either favorably or otherwise. The soil also holds varying quantities of gaseous matter and of water, which are important factors in its functions.