394 PURPLE DYEING, ANCIENT AND MODERN. 



1849, "Guimot's mettotl Las travelled round the world, supplanting all tlic blue 

 colors which had been previously employed by the cottou-printer." It must 

 be confessed, however, that this statement is not quite exact, for the manufac- 

 turers still experienced some difficulty in using ultramarine. At first the color 

 was, for the most part, not sufiiciently fine, and consequently it aftected both 

 the spreading- knife and the rollers. That difficulty was obviated by the use 

 of albumen, (the whites of eggs,) which thus became a by no means unimport- 

 ant article of trade. It is used to condense, and to aid in spreading, the color, 

 but requires some slight admixture of oil to prevent the decomposition which 

 the albumen, pure and simple, was found to produce. 



Ultramarine is used not only to produce a blue, but also a white. Every 

 housewife well knows that blue of some kind must be used to counteract that 

 yellowish tinge which Ihien and cotton goods acquire when Avashed. This use 

 of the blue color is familiarly called nshig the blue-bag, but using the whitening 

 bag Avould, in truth, be the more appropriate phrase. As a general thing the 

 blue-bag is used far too freely. The effect should not be, as it generally is, 

 to leave a blue tinge, but only to neutralize that yellow tinge with which we 

 unavoidably associate the idea of imperfect cleansing. Ultramarine is also of 

 important service in restoring linen and cotton yarns and fabrics to good color — 

 from two to three pounds of the color sufficing to restore fifty pieces of linen. 

 From ten to fifteen ounces are sufficient for the perfect bleaching of twenty 

 pounds of yarn, and so efiective is it in small quantities, and therefore so cheap, 

 that even whitewashers use it to give increased brightness and cleanness to 

 their white. 



It was formerly considered, on toxicological grounds, that the use of ultra- 

 marine in whitening sugar was objectionable. We need here only so for ad- 

 vert to the discussions of the public journals upon that point as to say that 

 two pounds and a half of ultramarine suffice to bleach fifty tons of sugar, being 

 just -^j^ grain to the pound, a proportion in which even that deadly corrosive, 

 arsenic, Avould be entirely innocuous. Whether the sulphuric-hydrogen gas, 

 which is liberated by the contact of the ultramarine in the sugar with the acid 

 in wine, be offensive, is a question Avhich we leave to the olfactories of the 

 chemist to decide. How far ultramarine is, or may be, adulterated, chemists, 

 we believe, have not, as yet, determined. Manufacturers maintain that it is 

 not merely right, but even necessary, to mix potter's clay and gypsum with 

 ultramarine, in order to get a lighter color; and to us it seems that, on that 

 point at least, the manufacturer is a better judge than the chemist. The pur- 

 chaser well knows that such admixture is made, and for what purpose, so that, 

 whether right or wrong, there is, at all events, no deception ; but if be wishes 

 no such admixture in the ultramarine which he purchases, a simple and facile test 

 of the quality is at hand. Adulteration is present if the color be not entirely 

 discharg(>d by strong acids, or if it change color when boiled in a ley of potash. 

 The adulteration in this latter case has been made by organic matters, for the 

 purpose of producing the fiery brilliancy of the natural ultramarine. If, to be 

 thus tested, the ley assume a greenish tinge, the ultramarine contains a super- 

 fluous amount of sul])hur natrium ; and if the ultramarine adheres in hard clots 

 or lumps the salts have not been sufficiently washed from it. When mere ap- 



f)carance is alone relied on as a criterion, the judgment, however practiced, is 

 iable to be mistaken, for there is no other color which afibrds so much scope 

 for visual deception. 



There arc two qualities to be regarded in the genuine ultramarine — the color- 

 ing and the covering quality — which maintain no direct ratio one to the other. 

 The coloring quality may be tested by mixing one part of ultramarine with 

 ten parts of any white color — white lead, for instance, or clay, or gypsum — and 

 then closely observing the tone of the mixture. These trials should never 

 be omitted by pm-chascrs, for in two ultramarines, whiclf to the sight appear 



