V. HYDROMETER < . 175 



The proof of the correctness is simple ; it is only necessary to have a good 

 pair of scales and some distilled water : 



650 weight = spindle 650 ; 

 spindle 0-650 +350 weight = spindle 1,000; 

 . spindle 1,000 + 400 weight = spindle 1,400. 



The construction of these areometers is new. Eor many years the exhibitor 

 had constructed similar areometers, consisting, however, of two spindles only, 

 which were very much liked, under the name of Wittstock's areometer, 

 on account of their accuracy ; but it was too fragile, owing to the light 

 spindle (there being but two of them) having to carry too much weight. 

 Moreover, the late Privy Councillor, Dr. Wittstock (apothecary to the Royal 

 Court at Berlin), had devised a peculiar proportionate weight to the same, 

 from which the spindles had derived their name, but which is now no longer 

 in use. 



The areometers constructed by the exhibitor, the normal weight of which 

 has been recommended by Mr. Hirsch, apothecary, at Giessen, and which 

 corresponds to the gram scale, have the following advantages, compared with 

 other similar instruments : 



They can be easily tested as to their accuracy (as shown before) ; they 

 will not be affected by the liquids ; they can be easily cleaned, and will 

 sink slowly and imiformly in any liquid, and are not surpassed, nor even 

 equalled, by most similar instruments, in respect of accuracy. 



One of the exhibited areometer-cases contains three spindles, which are 

 perfectly equal in point of accuracy with those in the second case. The 

 milky glass lines at the neck are, however, fastened only with sealing-wax, 

 which, in case of great carelessness, may dissolve, although persons of ex- 

 perience have used these spindles for years without injury; besides, every 

 particle of sealing-wax can be easily supplied as soon as any defect has been 

 noticed. But, in order to avoid this, the milky glass lines on the three 

 spindles in the second case have been melted together with the glass 

 plate. 



Besides the weights, there are added to the two cases a cylinder for 

 weighing the liquids, a pair of forceps for placing the weights, and a thermo- 

 meter for determining the temperature of the liquids, which latter is adapted 

 in its form and the strength of the glass to be used as a stirring rod. 



The exactness of the indications of Zorn's spindles affords also the advant- 

 age of testing the correctness of other liquid scales, such as Tralles, Baume, 

 and others made on a scientific basis. 



679. Alcoholometer. 



Siemens Brothers and Co., Charlottenburg. 



An apparatus for measuring simultaneously the quantity of spirit flowing 

 through it, and the per-centage of proof spirit contained in that spirit. The 

 quantity is measured by a revolving drum imparting motion to a counter 

 under the control of a hydrometer containing spirit such as is the average 

 production of the still. The measurement is unaffected either by the velocity 

 at which the spirit enters or by the friction of the bearings of the spindles of 

 the drum. 



679a. Metallic Alcoholometer, on Tralles's principle. 



VV. Gloukhoff, St. Petersburg. 



The metallic alcoholometer, with additional weights, newly adapted by the 

 Russian Government, is made on the principle of Sykes's hydrometer, but its 

 scale is adapted to the system of Tralles, legalized in Russia. 



