IM^t Mr Johnston's Visit to Berzelius, 



of which he gives at once to the late Assessor Gahn. The 

 execution at least is his own, for his own turning-lathe, and 

 his own tools, make all his contrivances in wood. Through 

 his whole laboratory indeed, may be seen marks of that same 

 scrupulous nicety which have made his analytical determina- 

 tions so valuable. In Sweden they have the benefit of glass 

 free from lead, and of a filtering paper made expressly for the 

 purpose, and unequalled in the world. It is made in winter, 

 and being hung up to dry in a frosty atmosphere, the water 

 freezes and makes it porous, so that while it is sufficiently close 

 to retain all undissolved matter, liquids pass through with 

 great rapidity. Its excellence, and the recommendation of the 

 Swedish chemists, have brought it into great request, and much 

 of it is in consequence exported. It contains no soluble mat- 

 ter, and leaves only 1-6000 of its weight of ashes. The usual 

 mode employed by Berzelius is to weigh his filter, and after 

 collecting his precipitate to burn it, allowing 1-6000 for the 

 weight of the ashes. A slight error here in the weight of the 

 filter it will be seen cannot afl]ect the result. He condemns 

 the mode of double filters unqualifiedly. It was formerly his 

 own way of operating, and he cannot bear that others should 

 follow a method he has long given up for its inaccuracy. De- 

 cantation he never employs, but collects always his precipitates 

 on the filter. For washing them he uses commonly the Sprut 

 Jlaska (squirt flask) with warm water. This is infinitely better 

 than the flask with cold water, inasmuch as it keeps up a con- 

 stant stream without the trouble of blowing into it, and at the 

 same time, serves all the purposes of the syringe recommended 

 by Faraday. If the aperture be small enough, there is not 

 the slightest risk of loss from little drops or sparkles flying off\ 

 While on the subject of manipulation, I may mention a method 

 of pouring which I learned also from Berzelius, and which 

 has many advantages over the rod. It is simply to touch 

 the edge of the glass at the spot to be poured from with a 

 little grease. The end of a candle does very well, or a bit of 

 tallow made into that shape, and covered with a small case to 

 prevent its soiling the fingers. By the use of this precaution 

 liquids may be poured with ease even from a wide mouthed 

 ye^5^1 withoiit. the loss of a drop. 



