CHAPTER XXV. 

 CHEMISTRY WITHOUT A LABORATORY. 



WE have already pointed out ,the possibility of going through a course of 

 physics without any special apparatus, we shall now endeavour to show our 

 readers the method of performing some experiments in chemistry without a 

 laboratory, or at any rate with only a few simple and inexpensive appliances. 

 The preparation of gases, such as hydrogen, carbonic acid, and oxygen, is 

 very easily accomplished, but we shall here point out principally a series of 

 experiments that are not so much known. We will commence, for example, 

 by describing an interesting experiment which often occurs in a course of 

 chemistry. Ammoniacal gas combined with the elements of water is 

 analogous to a metallic oxide which includes a metallic root, ammonium. 

 This hypothetically composed metal may be in a manner perceived, since it 

 is possible to amalgamate it with mercury by operating in the following 

 manner : We take a porcelain mortar, in which we pour a quantity of 

 mercury, and then cut some thin strips of sodium, which are thrown into the 

 mercury. By stirring it about with the pestle a loud cracking is produced, 

 accompanied by a flame, which bears evidence to the union of the mercury 

 and the sodium, and the formation of an amalgam of sodium. If this 

 amalgam of sodium is put into a slender glass tube containing a concen- 

 trated solution of hydrochlorate of ammonia in water, we see the ammonia 

 expand in an extraordinary manner, and spout out from the end of the tube, 

 which is now too small to contain it, in the form of a metallic substance 

 (fig- 302)- In this case, the ammonium, the radical which exists in the 

 ammoniacal salts, becomes amalgamated with the mercury, driving out the 

 sodium with which it had previously been combined ; the ammonium thus 

 united with the mercury becomes decomposed in ammoniacal gas and 

 hydrogen, the mercury assuming its ordinary form. Phosphate of ammonia 

 is very valuable from its property of rendering the lightest materials,' such as 

 gauze or muslin, incombustible. Dip a piece of muslin in a solution of 

 phosphate of ammonia, and dry it in contact with the air ; that done, you 

 will find it is impossible to set fire to the material ; it will get charred, but 

 yofl cannot make it burn. It is to be wished that this useful precaution were 

 oftener taken in the matter of ball-dresses, which have so frequently been the 

 cause of serious accidents. There is no danger whatever with a dress that 



