Experiments with Plants; A First School-Book of Science

Experiments with Plants; A First School-Book of Science

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ...is known as plant ash. Examine it. 1. What is its colour? 2. How does it feel to the touch? 3. Is it heavier or lighter than water? 4. Is it soluble in cold water? 5. Find out by litmus-paper whether the water you have mixed it with gives an acid or alkaline reaction. If it does, what light does this throw upon the solubility of the ash? In the preparation of the ash the leaves have been subjected to both drying and burning. The former process removes all the water, the latter most of the carbon. It is evident that these two substances account for most of the bulk of the fresh leaf. The ash, which can be neither evaporated nor burned, is a mere fraction of the dry weight of the leaf, and the dry weight is only a fraction (in some cases less than one-tenth) of the weight of the fresh leaf. Suppose in a particular case the weight of the ash to be 5 per cent. (which would be quite a possible proportion) of the dry weight, then a pound of fresh leaves or other material would yield rather more than one-twelfth of an ounce of ash. To get a pound of the ash we should require to burn 200 lb. weight ofleaves. A single leaf weighing 5 grammes (say 75 grains) would on the above basis yield 25 milligrammes (less than half a grain) of ash. More than this, the ash contains many compounds, and so the proportion of anyoneof these ingre dients becomes more insignificant still. It would, however, be a great mistake to estimate the value of any particular substance by the small amount of it present in the ash. The presence or absence of a few grains of certain chemical compounds settles whether a plant will be healthy and grow or fade and die. We proceed now to apply chemical tests to see what the ash contains. As a rule, in working through these, only small..show more

Product details

  • Paperback | 46 pages
  • 189 x 246 x 3mm | 100g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236869850
  • 9781236869852