^^72 Scientific Intelligence. [Jan. 



Article XV. 



SCIENTIFIC INTELLIGENCE, ANP NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Test for Bari/tes and Slroritia. 



Ba'-ytes and strontia may be readily distinguished from each other by the 

 fbllowins: process: Make a solution of the earth, whichever it may be, either 

 by niirir, muriatic, or some other acid, which will form a soluble salt with it: 

 add solution of sulphate of soda in excess, filter, and then test the clear fluid by 

 subcarhonate of potash. If any precipitate falls down, the earth was strontia; 

 if the fluid .remains clear, it was barytes. — (Journal of Science and the Arts, 

 vol. X. p. l'89.) 



II. Ammoniacal Alum. 



M. Anatole Riffault has detailed a set of experiments made upon ammoniacal 

 alum. No analysis of this salt, he states, is to be found in any treatise on 

 chemistry. He observes also that a knowledije of its composition is necessary 

 to make an exact analysis of the different varieties of alum, some of which con- 

 tain a quantity of this salt, especially those which are not manufactured in 

 France, llavinj^ purified the anunoniacal alum of commerce by repeated crys- 

 tallizations, so as to free it from iron, it was dried by exposure to the air; 

 13 gr. 420 ()f this salt were first gently, and afterwards strongly, heated in a pla- 

 tina crucible for an hour and a half; the residuum was pure alumina; it 

 weighed 1 lt. 603, equal to 1 1-944 per cent. On repeating the experiment, the 

 alumina amounted to 11 869 per cent, giving a mean of 1 1*906 per cent, of 

 alunnna in ammoniacal alum. 



To determine the quantity of sulphuric acid, a solution of 6 gr. 522 of the 

 alum was decomposed by muriate of barytes; the sulphate weighed 7 gr. 010, 

 = 2 gr. 3547 of sulphuric acid, or 36-104 per cent. This experiment on repe- 

 tition gave 35-991 per cent, or a mean of 36 042. 



M. Itiffanlt concludes, that in the ammoniacal alum 11*906 of alumina are 

 combined with 26-979 of sulphuric acid, the remaining 9 063 of the acid 

 uniting with 3 898 of ammonia. The composition of ammoniacal alum he, 

 therefore, states to be : 



Sulphate of ammonia 12*96 1 



alumina 38 885 



Water 48*154 



100*000 



The atomic constitution of this salt he considers as 



One atom of sulphate of ammonia 7167 .... 12*838 



Three atoms ot sulphate of alumina 216*69 .... 38*816 



Twenty-four atoms of water 269*88 48 316 



558'24 100*000 



In the next number of the Annah I shall probably state the results of some 

 experiments which i. have made on alum, including the ammoniacal alum above- 

 ,,?iBeutioued. 



III. Sulphate of Indigo a$ a Test to determine the Strength of Solutions ofOxy^ 



7nuriute of Lime. 

 It is well-known that bleaciiers who employ solution of oxymuriate (chloride) 

 of lime, are in the practice of determining its strength by the quantity of a givea 



