594 FOODS AND FOOD ADULTERANTS. 



has been added a little hydrochloric acid. The whole is transferred to a 

 500-cubic centimeter flask and after cooling made up to the mark and 

 filtered. Of the filtered liquid 100 cubic centimeters, representing 1 

 gram of the sample, are measured out, heated in the water bath, and 

 slight excess of barium chloride added; then without filtering barium 

 hydrate is added in slight excess, the precipitate filtered off and washed. 

 To the filtrate is added a little ammonium hydrate and then ammonium 

 carbonate until all the barium is precipitated. This precipitate is fil- 

 tered and washed, the filtrate evaporated to dryness and carefully igni 

 ted until all volatile matter is driven off, when it is weighed. This gives 

 the weight of the mixed chlorides. The residue is taken up with hot 

 water, from 5 to 10 cubic centimeters of a 10 per cent, solution of 

 platinic chloride added, and the whole evaporated to a sirupy con- 

 sistence in the water bath ; then it is treated with strong alcohol, the 

 precipitate washed with alcohol by decantation, transferred to aGooch 

 crucible, dried at 100 C., and weighed. The weight of the precipitate 

 multiplied by .19308 gives the weight of K 2 O, and by .3056 the equiva- 

 lent amount of KC1. The weight of KC1 found is subtracted from the 

 weight of the mixed chloride, the remainder being the NaCl, which mul- 

 tiplied by .5300 gives the weight of Na 2 O in the sample. 



ESTIMATION OF ALUMINIUM. 



In the case of a " straight" alum powder, the simple estimation by 

 burning to ash, extracting, and determining the alum by direct precip- 

 itation with ammonia would probably be accurate, but in view of the 

 frequent use of flour as a " filler,' 1 as well as of the presence of calcium 

 as an impurity, it is best, even with those made up with alum alone, 

 to use a method which will insure a complete separation of the alum. 

 The following procedure, given by Allen for the quantitative estimation 

 of alum in bread, was found to give good results with baking-powders: 



Take 5 grams and incinerate in a muffle. The heat should be mod- 

 erate so as not to fuse the ash. The process is completed by adding 

 pure sodium carbonate and a little niter, and heating the mixture to 

 fusion. The product is rinsed out with water into a beaker, acidulated 

 with hydrochloric acid, and evaporated to dryness. The residue is 

 taken up with dilute acid, the liquid made up to 500 cubic centimeters 

 in a graduated flask, filtered, and 50 cubic centimeters taken for pre- 

 cipitation. To the solution dilute ammonia is added until the precipi- 

 tate barely redissolves on stirring, when a slightly acid solution of am- 

 monium acetate is added, and the liquid brought to a boil. After a few 

 minutes' heating the solution should be set aside for some hours, when 

 its appearance should be observed. (If gelatinous it probably consists 

 solely of iron and alum phosphates, but if granular more or less of the 

 earthy phosphates have been co-precipitated; then it should be sepa- 

 rated, redissolved in dilute hydrochloric acid, the solution again neu- 

 tralized with ammonia, and treated with ammonium acetate.) Thepre- 



