266 METHODS OF ANALYSIS [Chap, 



slowly, with constant stirring, 2 cc. of hydrochloric acid (2 to 1). Keep the mixture 

 in the freezing bath 15 minutes. Filter off the crystals formed, using suction, and 

 wash with 95% alcohol by volume. Return the combined filtrate and washings 

 to the freezing bath for 15 minutes. Filter off the crystals formed, using the origi- 

 nal filter paper. Wash the combined crops of crystals thoroughly with alcohol. 

 Dry at room temperature and dissolve in a minimum amount of chloroform. Add 

 methyl alcohol to the chloroform solution, a little at a time, until the nitroso- 

 chlorids crystallize out, mount the separated and dried crystals in olive oil and 

 examine under the microscope. Pinene nitroso-chlorid crystals have irregular 

 pyramidal ends while limonene nitroso-chlorid crystallizes in needles. 



ALMOND EXTRACT. 



41 ALCOHOL.-TENTATIVE. 



Inasmuch as almond extract usually contains only about 1% of almond oil 

 the alcohol can, in most cases, be calculated from the specific gravity of the 

 extract. If the extract is high in solids, determine the alcohol as follows: Add 25 

 cc. of the extract, measured at 20°C., to 75 cc. of saturated sodium chlorid solution 

 in a separatory funnel and extract twice with 50 cc. portions of petroleum ether 

 (b. p. 40°-60°C.). Collect the petroleum ether extract in a second separatory fun- 

 nel and wash twice with 2 portions (25 cc.) of saturated brine. Combine the origi- 

 nal salt solution with the washings; add a little powdered pumice and distil into a 

 100 cc. flask. When almost 100 cc. have been distilled, make up to the mark with 

 v/atcr at 20°C. and determine alcohol from the specific gravity, as directed under 

 XVII, 4. 



BENZALDEHYDE.— TENTATIVE. 



42 REAGENT. 



Phenylhydrazin solution. — Add 1.5 cc. of glacial acetic acid to 20 cc. of water and 

 mix with 1 cc. of phenylhydrazin. 



43 DETERMINATION. 



Measure out 2 portions of 10 cc. each of the extract into 300 cc. Erlenmeyer 

 flasks and add 10 cc. of the phenylhydrazin solution to 1 flask and 15 cc. to the 

 other. Allow to stand overnight in a dark place, add 200 cc. of water and filter on 

 a tared Gooch crucible, provided with a thin layer of asbestos. Wash first with cold 

 water, finally with 10 cc. of 10% alcohol, and dry for 3 hours in a vacuum oven at 

 70°C., or to constant weight over sulphuric acid. The weight of the precipitate 

 multiplied by the factor 5.408 gives the weight of benzaldehyde in 100 cc. of the 

 sample. If duplicate determinations do not agree, repeat the operation using a 

 larger quantity of the phenylhydrazin solution. 



HYDROCYANIC ACID. 



44 Qualitative Test. — Tentative. 



Add several drops of ferrous sulphate solution and a single drop of ferric chlorid 

 solution to several cc. of the extract. Mix thoroughly, add sodium hydroxid solu- 

 tion, drop by drop, until no further precipitate forms and then dilute hydro- 

 chloric acid to dissolve the precipitated hydroxids. In the presence even of small 

 amounts of hydrocyanic acid, a Prussian blue coloration or suspension will develop. 



