100 Professors Kirchhoff and Bunsen on Chemical 



experiment, a quantity of strontium may be thus detected equal 

 to the j^^ part of a milligramme in weight. 



The chlorine and the other haloid salts of strontium give the 

 best reaction. The hydrated oxide and the carbonate of stron- 

 tium give the action less vividly, the sulphate less distinctly, 

 whilst the compounds of strontium with the non-volatile acids 

 give either a very slight reaction or else none at all. Hence it 

 is well first to bring the bead of substance alone into the flame, 

 and then again after moistening with hydrochloric acid. If it 

 be supposed that sulphuric acid is present in the bead, it must 

 be held in the reducing part of the flame before it is moistened 

 with hydrochloric acid, for the purpose of changing the sulphate 

 into the sulphide, which is decomposed by hydrochloric acid. In 

 order to detect strontium when combined with silicic, phospho- 

 ric, boracic, and other non-volatile acids, the following course of 

 procedure gives the best results. Instead of fusing with carbo- 

 nate of sodium in a platinum crucible, a conical spiral of plati- 

 num wire is employed ; this spiral is heated to whiteness in 

 the flame, and dipped whilst hot into finely powdered dried 

 carbonate of sodium, which properly should contain so much 

 water that a sufficient quantity adheres to the wire when it is 

 once dipped into the salt. The fusion takes place in this spiral 

 much more quickly than in a platinum crucible, as the mass of 

 platinum requiring heating is small, and the flame comes into 

 direct contact with the salt. As soon as the finely powdered 

 mineral has been brought into the fused soda by means of a 

 small platinum spatula, and the mass retained above the fusion 

 point for a few minutes, the cooled mass has only to be turned 

 upside down, and knocked on the porcelain plate of the lamp 

 in order to obtain the salt in one coherent bead. The fused 

 mass is covered by a piece of writing-paper, and then broken by 

 pressing it with the blade of a steel spatula until the whole is in 

 the state of a fine powder. The powder is collected to one spot 

 on the edge of the plate, and carefully covered with hot water, 

 which is allowed to flow backwards and forwards over it, so that, 

 after decanting and rewashing the powder several times, all the 

 soluble salts are extracted without losing any of the residue. If 

 a solution of chloride of sodium be employed instead of water, 

 the operation may be conducted still more rapidly. The inso- 

 luble salt contains the strontium as carbonate ; and one or two 

 tenths of a milligramme of the substance, brought on to the 

 wire and moistened with hydrochloric acid, is sufficient to pro- 

 duce the most intense reaction. It is thus possible, without help 

 of platinum crucible, mortar, evaporating basin, or funnel and 

 filter, to fuse, powder, digest, and wash out the substance in the 

 space of a few minutes. 



