36 THE BOOK OF THE LANTERN. 



indeed, dangerous ; for carbonaceous material, when mixed 

 with, the chlorate, constitutes a very powerful explosive. 

 (As an instance of this, I may mention that in the greatest 

 explosion of modern times, when thousands of tons of 

 explosive material were fired for the purpose of destroying 

 the "Hell-Gate Bock" at the entrance of New York 

 Harbour, a large proportion of the chemicals employed 

 consisted of chlorate of potash combined with coal-dust.) 

 Before mixing the ingredients together, therefore, the 

 crystals of potash should be carefully picked over by hand, 

 and any unconsidered trifles which have no business to be 

 present should be carefully extracted from it. A little care 

 is also necessary with regard to the manganese. Accidents 

 have happened from lampblack, bone-dust, and other similar 

 compounds, having been substituted (let us hope by acci- 

 dent) for the manganese that was intended to be used. In 

 buying fresh samples, therefore, of manganese, it should 

 be carefully tested, and the best way of doing this is to mix 

 up a small quantity of the potash and the manganese in 

 the proportions above given, and to put them in a test 

 tube, which should be held over the flame of a spirit lamp. 

 If the mixture simply sparkles while oxygen gas is given 

 off at the mouth of the tu-be (as may be tested by the spark 

 on a blown-out match), the mixture is safe ; but if any- 

 thing in the least resembling an explosion should take place, 

 the manganese is wrong, and must be rejected. But the 

 operator is not liable to fall into the error of mistaking 

 lampblack or bone-dust for manganese, because they are, 

 bulk for bulk, so very much lighter than that heavy 

 earth. 



