APPENDIX B. 387 



Gum (arable'). For establishing the addition of any considerable quantitiesof gum 

 4cc. wine are treated with lOcc. of 96 per cent, alcohol. If gum is present, the 

 mixture becomes milky, and only clears up again after several hours. The precipi- 

 tate which occurs adheres partly to the sides of the tube, and forms hard lumps. In 

 genuine wine flakes appear after a short time, which soon settle, and remain some- 

 \vhat loose. For a more exact test it is recommended to evaporate the wine to the 

 consistency of a sirup, extract with alcohol of the strength given above, and dissolve 

 the insoluble residue in water. This solution is treated with some hydrochloric acid 

 (of specific gravity 1.10) heated under pressure two hours, and the reducing power 

 ascertained with Fehling's solution, and calculated to dextrose. In genuine wines 

 no considerable reduction is obtained in this way. (Dextrin is to be detected in 

 the same way.) 



Mannite. As the presence of manuite in wines has been observed in a few cases, it 

 should be considered when pointed crystals make their appearance in the extract or 

 the glycerine. 



Nitrogen. In the estimation of nitrogen the soda-lime method is to be used. 



Mineral matters. For their estimation 50cc. of wine are used. If the incineration 

 is incomplete, the charcoal is leached with some water, and burned by itself. The 

 solution is evaporated in the same dish, and the entire ash gently ignited. 



Chlorine estimation. The wine is saturated with sodic carbonate, evaporated, the res 

 idue gently ignited and exhausted with water. In this solution the chlorine is to be 

 estimated volumetrically accordin to Volhard, or gravimetrically. Wines whose 

 ashes do not burn white by gentle ignition iisually contain considerable quantities 

 of chlorine (salt). 



Sulphuric acid. This is to be estimated directly in the wine by the addition of 

 barium chloride. The quantitative estimation of the sulphuric acid is to be carried 

 out only in cases where the qualitative test indicates the presence of abnormally 

 large quantities. (In the case of viscous or very muddy wines a previous clarification 

 with Spanish-earth is to be recommended.) 



If in a special case it is necessary to investigate whether free sulphuric acid or 

 potassium bisulphate are present, it must be proved that more sulphuric acid is pres- 

 ent than is necessary to form neutral salts with all the bases. 



Phosphoric acid. In the case of wines whose ashes do not react strongly alkaline 

 the estimation is made by evaporating the wine with sodic carbonate and potassic 

 nitrate, the residue gently ignited and taken up with dilute nitric acid; then the 

 molybdenum method is to be used. If the ash reacts strongly alkaline the nitric- 

 acid solution of it can be used directly for the phosphoric-acid determination. 



The other miaeral constituents of wine (also alum) are to be determined in the ash 

 or residue of incineration. 



Sulphurous acid. One hundred cubic centimeters wine are distilled in a current of 

 carbouic acid gas after the addition of phosphoric acid. For receiving the dis- 

 tillate 5cc. of normal iodine solution are used. After the first third has distilled 

 off, the distillate, which must still contain an excess of free iodine, is acidified with 

 hydrochloric acid, heated and treated with barium chloride. 



Adulteration of grape wine with fruit ivine. The detection of this adulteration can 

 only exceptionally be carried out with certainty by means of the methods that have 

 so far been offered. Especially are all methods untrustworthy which rely upon a 

 single reaction to distinguish grape from fruit wiue ; neither is it always possible to 

 decide with certainty from the absence of tartaric acid or from the presence of only 

 very small quantities that a wine is not made from grapes. 



In the manufacture of artificial wine together with water the following articles are 

 known to be sometimes used: Alcohol (direct or in the shape of fortified wine), cane 

 sugar, starch sugar, and substances rich in sugar (honey), glycerine, bitartate of 

 potash, tartaric acid, other vegetable acids, and substances rich in such acids, sali- 

 cylic acid, mineral matters, gum arable, tauuic acid, and substances rich in the same 

 (e. </., kino, catechu), foreign coloriug matters, various ethers and aromas. 



