120 



ia a general way for commercial purposes ; it suffices to determine.the 

 proportion of moisture, starch, gluten, and sugar, as well also as the 

 mineral salts which may have been added for purposes hereinafter to 

 be desci'ibed. 



These salts may be determined in the following manner, with suffi- 

 cient accuracy : — a proportion of suspected flour is triturated in a sieve 

 with water, as above described, the milky fluid being collected in a 

 conical shaped glass: when the starch has thoroughly subsided the clear 

 liquor is decanted off, boiled and filtered ; to one portion hydrochloric 

 acid and ammonia are carefully added, when, if alum be present, a 

 more or less copious gelatinous precipitate will be produced : this is 

 aluviina. To the other portion chloride of barium is added, when a 

 white precipitate will be formed if sulphuric acid be present ; and 

 these two re-actions are conclusive evidence of the presence of alum, 

 the quantity being calculated from the weight of aluminous preparation 

 obtained from the whole quantity of liquor. 



The starchy deposit is dried in its conical glass, from which it is 

 then readily removed. The tip of the cone, which of course will con- 

 tain all the denser matters, is removed and digested in cold water ; the 

 clear liquor is filtered off, and tested with chloride of barium aud oxalate 

 of ammonia ; white precipitates with these re-ageuts clearly prove the 

 presence of sulphate of lime, or gypsum. The residue left after digest- 

 ing the deposit in water is treated with hydrochloric acid ; effervescence 

 indicates the presence of chalk, which must be confirmed by the addi- 

 tion of oxalate of ammonia to the filtered solution, which will give a 

 precipitate if lime be present. 



Besides these tests a portion of the flour must be boiled in water 

 slightly acidulated with hydrochloric acid ; or, what is better, burn 

 and calcine the ash of a portion of the flour, and treat it with dilute 

 acid, filter, and add acetate of potass with a few drops sesqui-chloride of 

 iron ; if bones have been mixed with the flour, a copious white precipi- 

 tate of phosphate of iron is produced. 



Various chemical tests have been proposed for detecting admixtures 

 of other farinaceous substances with bread and flour, but having found 

 that the microscope furnishes the readiest and more certain results, we 

 have deemed it sufficient to confine ourselves to its indications. 



Having submitted many samples of flour in this way to examination, 

 we have found that, as a rule, the public are supplied with a genuine 

 article, although au occasional exception has come under our notice. 

 Thus, we remember some time ago examining a sample of flour which 

 had evidently been prepared from, or largely admixed with, damaged 

 wheat, as a vast proportion of the starch grains were ruptured, aud 



