ATTRACTION. J77 



d.) Weighing. Scales, coarse and fine, very sensible balances. 

 e.) Sifting. Selves, of various fineness, with andwithout covers. 

 /.) Decantation. Syphons, coffee pots, &ic. 

 g.) Filtration. Unsized paper of various quality, pounded glass, 

 flannel, filtering stones, sand, &c. Filtering funnels and stands. 



6. LUTES. 



Flour and water, rye paste ; sand, flour and clay ; fat lute, com- 

 posed of clay and oil, lime and white of an egg. 



7. VESSELS FOR KEEPING PRODUCTS. 



Ground glass stopped bottles for deliquescent salts ; wide mouth- 

 ed bottles ; common vessels of any description. Tin cases for phos- 

 phorus bottles. 



Drawers, mineralogical cabinet, bladders and silk bags, for the pur- 

 pose of administering gases. 



8. LABORATORY general idea of one. Any convenient, light, dry, 

 and well ventilated place for the performance of experiments. Neat- 

 ness, order, and care of one's person and clothes and premises are in- 

 dispensable. 



Necessity of caution and presence of mind. Unreasonable fears 

 of chemical experiments. Frequent ventilation of a laboratory ne- 

 cessary. 



Specific gravity. 



The specific gravity of a body is its weight under a given volume. 

 It is often necessary in chemical experiments, to take the specific 

 gravity of bodies. Ample instructions are given on this subject, in 

 every book of Natural Philosophy, and for the present, mention will 

 be made only of its application to gaseous bodies. 



It may however be stated, for the sake of those who have not 

 more delicate apparatus, that common money scales are sufficiently 

 exact for most purposes. A fragment of the substance to be weigh- 

 ed, may be suspended by a fine thread or piece of sewing silk, from 

 the point of bearing of one arm of the balance, the thread being 

 long enough to allow the fragment to swing below the scale so as to 

 admit of immersion in pure water ; we then proceed as is usual in 

 similar cases. Dr. Hare has several ingenious contrivances and in- 

 ventions for taking specific gravities, which may be seen in his com- 

 pendium, and in the American Journal of Science, and if there is 

 room, they may be given in an appendix to this work. 



The specific gravity of fluids is easily taken by weighing them in 

 a thin vial with a narrow neck, having a mark upon it so that the same 

 volume may be easily taken ; it is most convenient that the vial should 

 hold 1000 grains of distilled water. 



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