Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: dissolve in water' and test for phosphoric acid by nitric acid and ammonium molybdate. At once or after warming a yellow precipitate will appear. 119. Use a small portion for the acrolein test (91). 120. What do each of the above tests show about the molecular composition of lecithin? THE PROTEINS. The protein compounds constitute the greater part of the solid matter of the blood, muscles, nerves, and other organs of the animal body. The urine, tears, and perspiration, in a normal condition, never contain more than a trace. The proteins contain carbon, hydrogen, nitrogen, oxygen, and usually sulphur. Some contain phosphorus and a few others iron. When heated they are charred, giving off water, inflammable gases, and ammonia, at the same time emitting a strong odor, similar to that of burnt horn or wool. Upon further ignition they leave an ash, though whether this was originally a part of the protein molecule has. not been decided. They are often spoken of simply as the nitrogenous constituents of the body or the food, although not all of the nitrogenous compounds found there belong to this class. The proteins are very complex substances with a high molecular weight, and it is probably owing to this fact that they are so easily decomposed, as is seen by the putrefaction which sets in soon after life has ceased. To the large molecule, too, is due the inability of most of them to pass through a parchment or animal membrane. GENERAL PROPERTIES OF THE PROTEINS. 121. Burn a small piece of dry albumin or other protein compound on a piece of porcelain or platinum foil,or on a wire. Notice that it turns black from the presence of carbon. Observe the characteristic odor. On continued heating it will all disappear except the mineral matters, or ash. 122. What is the r...